Operation Manual Beta-Secondary Standard 2 (BSS-2)...“interface” is illuminated when the BSS 2 is controlled by the computer. The control unit also includes additional independent

Operation Manual

Beta-Secondary Standard 2

(BSS-2)

Eckert & Ziegler

Nuclitec GmbH

Gieselweg 1

38110 Braunschweig

Germany

Tel. +49 5307 932-0

Fax +49 5307 932-272

[email protected]

www.ezag.com

BSS-2

Operation Manual

BSS2 - Operation Manual as of 24th April 2013 Page 1 of 46 Pages

CONTENT

1 INTRODUCTION ............................................................................. 3

1.1 COMPONENTS OF THE BETA SECONDARY STANDARD 2 ........................ 4 1.1.1 Source set ......................................................................................................... 4

1.1.2 Irradiation device ............................................................................................... 5

1.1.3 Control unit ........................................................................................................ 6

2 SAFETY INSTRUCTIONS .............................................................. 7

3 SETTING UP THE BETA SECONDARY STANDARD 2 ................ 8

3.1 MOUNTING OF THE BETA SECONDARY STANDARD ................................. 8 3.1.1 Assembling the irradiation device ..................................................................... 9 3.1.1.1 Horizontal operation ................................................................................................................................... 9 3.1.1.2 Vertical operation........................................................................................................................................ 9

3.1.2 Connecting the control unit ............................................................................. 12 3.1.2.1 Power supply ............................................................................................................................................ 12 3.1.2.2 Control and data cables ............................................................................................................................ 12 3.1.2.3 Safety circuit ............................................................................................................................................. 13

3.2 Software installation ..................................................................................... 14

3.3 Software operation........................................................................................ 14

3.4 Software configuration ................................................................................. 15 3.4.1 Language ........................................................................................................ 16

3.4.2 Decimal separators ......................................................................................... 16

3.4.3 Computer ports ............................................................................................... 17 3.4.3.1 Printer and serial port ............................................................................................................................... 18 3.4.3.2 Network Interface ..................................................................................................................................... 19

3.4.4 Source Data .................................................................................................... 19

3.4.5 Conversion coefficients ................................................................................... 21

3.4.6 Analogue to digital converter ........................................................................... 22

3.4.7 Angle sensor ................................................................................................... 22

3.4.8 Sensor Adjustment (Temperature, pressure, and humidity measurement) ..... 23

4 OPERATING THE BETA SECONDARY STANDARD 2 .............. 24

4.1 Introduction ................................................................................................... 24 4.1.1 Source stand ................................................................................................... 24

4.1.2 Turntable ......................................................................................................... 25

4.1.3 Filter holder ..................................................................................................... 25

4.1.4 Installing a source holder ................................................................................ 26

4.2 Positioning the dosimeter or phantom ....................................................... 27

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4.3 Irradiation with the BSS 2 ............................................................................. 30 4.3.1 Record File ...................................................................................................... 30

4.3.2 Irradiation ........................................................................................................ 30 4.3.2.1 Irradiation with dose indication ................................................................................................................. 33 4.3.2.2 Irradiation with dose rate indication .......................................................................................................... 34

5 QUALITY CONTROL .................................................................... 35

5.1 To test the sensors ....................................................................................... 35

5.2 Shutter test .................................................................................................... 35

5.3 Calibration ..................................................................................................... 36 5.3.1 Source calibration ........................................................................................... 36

5.3.2 Sensor Adjustment (temperature, pressure, and humidity measurement) ...... 36 5.3.2.1 Analogue to digital convertor calibration ................................................................................................... 36 5.3.2.2 Atmospheric pressure ............................................................................................................................... 38 5.3.2.3 Temperature ............................................................................................................................................. 39 5.3.2.4 Humidity ................................................................................................................................................... 39

5.4 Maintenance .................................................................................................. 41

5.5 Malfunctions .................................................................................................. 41

5.5.1 Failure of the shutter ....................................................................................... 41

5.5.2 Shutter cannot be opened ............................................................................... 42

5.5.3 Communication with the atmospheric pressure sensor is interrupted ............. 42

5.6 Sources exchange ........................................................................................ 42

6 TECHNICAL DATA ....................................................................... 43

6.1 Specification of beta sources, beam flattening filters and calibration distances ....................................................................................................... 43

6.2 Safety circuit ................................................................................................. 44

6.3 Turntable plate .............................................................................................. 45

6.4 Loading capacity of the turntable ................................................................ 46

6.5 Cable lengths ................................................................................................ 46

6.6 Supply voltage .............................................................................................. 46

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1 INTRODUCTION This operation manual is only valid for the BSS 2 software version 4.0 or higher. The Beta Secondary Standard 2 (BSS 2) can be used to irradiate dosimeters using beta particles emitted by Sr-90/Y-90, Kr-85, Pm-147 and Ru-106/Rh-106 (planned). The dose rates from the sources are calibrated at the Physikalisch-Technische Bundesanstalt (PTB) and are directly traceable to the primary standard for the dose of beta radiation in tissue. BSS 2 complies with the recommendations of ISO 6980. A scientific paper was published in J. Instrum. 2, P11002 (2007) „http://iopscience.iop.org/1748-0221/2/11/P11002“, substantial extensions are described in J. Instrum. 6, P11007 (2011) and corresponding Erratum and Addendum „http://www.ptb.de/de/org/6/63/f_u_e/bss2cons.pdf“. The properties of the radiation fields (spectra and beam homogeneities) are published in detail in J. Instrum 8, P02019 (2013) „http://iopscience.iop.org/1748-0221/8/02/P02019“. This manual intends to assist the user in setting up and operating the BSS 2. The irradiation procedure is controlled by a personal computer which stores the calibration data for the sources used. The user only has to select the measurement parameters, the irradiation conditions and the desired dose.

Figure 1: Beta Secondary Standard 2 (picture: Physikalisch-Technische Bundesanstalt - PTB)

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1.1 COMPONENTS OF THE BETA SECONDARY STANDARD 2 1.1.1 Source set The source set of the BSS 2 consists of three sources (Sr-90/Y-90, Kr-85 and Pm-147). Each source is mounted in a separate shielded holder with a shutter. The shutter has been designed so that it can be opened only when the source holder is mounted on the instrument, to prevent accidental exposure of staff. The dose rate on the surface of the source holder is less than 0.5 mSv/h so the holders can be handled for short periods without tongs.

Figure 2: Source Holder

The source holders must be kept in their transport and storage containers when not in use. Each source is supplied with a matching beam flattening filter as required by ISO 6980. The dose rate delivered at the irradiation position depends on the thickness of the filter, so the source and filter are calibrated as a pair at the PTB. The source holder and beam flattening filter have unique identifiers which are detected and checked by the BSS 2 system to prevent a wrong filter being used. With one BSS 2 up to four different source sets can be used.

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Figure 3: Beam Flattening Filters with Filter Identity Cards

1.1.2 Irradiation device The BSS 2 can irradiate dosimeters at a choice of fixed distances (11, 20, 30 and 50 cm) with the dosimeter orientated at different angles. The irradiation device consists of a source stand which is mounted on a linear guiding. In use, the source holder containing the radioactive source is locked into a bracket on the stand. The beam flattening filter is positioned in front of the source on location pegs. The effect of scattered betas by the source stand is negligible. A red flash light (positioned at the top of the source stand) is illuminated when the source is exposed or the shutter is not completely closed. The source stand can be positioned at accurately reproducible distances from the dosimeter. Sensors built into the linear guiding detect the position of the source stand along the guiding. The dosimeter to be irradiated is positioned on a turntable which can be rotated in 5° steps. The plate of the turntable must not be removed. The instrument can be assembled so that the linear guiding is either horizontal or vertical.

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1.1.3 Control unit The control unit contains all electronic components necessary to operate the BSS 2 including the sensor for atmospheric pressure. A separate sensor for measuring temperature and humidity is connected to the control unit using a cable (maximum length 5 m). The control unit is connected to the linear guiding/source stand using a special cable (maximum length 5 m). The irradiation procedure is controlled by a personal computer which is connected to the control unit either by a standard printer port or a network interface (TCP/IP). Via the chosen printer port both the BSS2 and a printer can be controlled. A red LED “interface” is illuminated when the BSS 2 is controlled by the computer. The control unit also includes additional independent circuitry for safety devices (a door switch and two further contacts for separate alarm systems). The LEDs on the control unit indicate whether the output voltages of the power supply are present and the status of the shutter and safety circuit (see section 3.1.2.3).

Figure 4: Control Unit

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2 Safety instructions The BSS 2 includes a set of high activity beta sources. Users must comply with all local regulations concerning storing and using such sources. The instrument must only be used for the application described in this manual. The instrument must be operated by appropriately qualified and experienced staff. The source holders have been designed to reduce the doses received by users as far as reasonably practicable if used under normal laboratory conditions. The BSS 2 must only be used with the sources supplied. Source holders must not be modified or tampered with. The source holders must be stored in the supplied transport container (or similar container) when not in use. Access to the sources must be controlled to prevent unauthorised use or theft. Before delivery the sources are tested for leakage following the requirements of ISO 9978 (Sealed Radioactive Sources - Leakage Test Methods). Leak tests must be carried out at regular intervals in accordance with local regulations (usually annually). The recommended working life of the sources is 10 years. The BSS 2 is equipped with a safety circuit to prevent accidental exposure of staff during irradiation. The user is responsible for assembling the circuit in accordance with local regulations. The BSS 2 can operate only once the safety circuit has been connected (see section 3.1.2.3 or section 6.2). Please also note that the beam flattening filters are mounted on thin rods which could cause injury if handled carelessly. The BSS 2 must be used with the software that is pre-installed (or its updates) on the personal computer supplied. No other programs should be installed on the personal computer. Any problems which arise as a result of installing other software are the responsibility of the user. The "Power Save" function of the PC which is connected to the BSS 2 must be switched off.

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3 SETTING UP THE BETA SECONDARY STANDARD 2

3.1 MOUNTING OF THE BETA SECONDARY STANDARD

source stand

profile bar for vertical operation

fastening bolts for profile bar

distance rod

turntable with displacement device

long spacer with fastening bolts for gas-filled damper (turntable side)

gas-filled damper (for vertical operation only)

short spacers with fastening bolts for gas-filled damper (source stand side)

temperature and humidity sensor

support feet with fasten-ing bolts (turntable side)

support feet with fastening bolts (source stand side)

Figure 5: Dismounted Components

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3.1.1 Assembling the irradiation device The BSS 2 can be assembled so that the linear guiding is either horizontal or vertical. 3.1.1.1 Horizontal operation For horizontal operation, the two support feet should be mounted under the linear guiding. The feet should be bolted to the threaded sliding blocks which are located in the groove on the bottom surface of the guiding (four 20 mm long M8 bolts are included for this). The feet should be positioned at opposite ends of the linear guiding. 3.1.1.2 Vertical operation

Figure 6: BSS 2 mounted for Vertical Irradiation

For vertical irradiation, the linear guiding is supported on a bar mounted on the linear guiding by the dosimeter turntable. To install the bar, first remove the plastic cover on the end of the linear guiding (four 10 mm long M4 bolts). Next, fit the bar using the four 120 mm long M8 bolts. The bar must be fixed in the same direction as the source stand (see Figure 7).

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Figure 7: Mounting the bar for vertical operation

The support feet should then be bolted to the threaded sliding blocks located in a groove on the bar (two 20 mm long M8 bolts for each). The feet should be positioned at opposite ends of the bar.

Figure 8: Mounting of the support feet

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Operation Manual


Finally, the source stand should be locked in the 50 cm irradiation position. Fit the gas-filled damper to the source stand (using the short spacers and M6 bolts provided - Figure 9) and to the linear guiding (using the long spacers and M6 bolts - Figure 10). The gas-filled damper allows the source stand to move smoothly from one irradiation position to another.

Figure 9: Fitting the gas-filled damper to the source stand

Figure 10: Fitting the gas-filled damper to the linear guiding

Figure 11: Mounted gas-filled damper

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3.1.2 Connecting the control unit 3.1.2.1 Power supply

The control unit will be factory set for the mains power supply of the country to which the instrument is delivered. Caution: If the power supply is set up incorrectly the instrument will malfunction or may be damaged. Any modifications must be made by qualified personnel only. 3.1.2.2 Control and data cables

The BSS 2 should be connected using only the cables supplied with the equipment.

computer safety circuit atmospheric pressure sensor

printer temperature and irradiation (optional) humidity sensor device

Figure 12a: Rear Panel of the Control Unit (old version)

Figure 12b: Rear Panel of the Control Unit (new version with Ethernet interface)

A new figure follows as soon as the new devices are supplied.

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The cables are designed so that each cable can only be connected to one socket of the control unit. Once the BSS 2 shall be connected to the computer via parallel and serial port, the cable for connecting the personal computer to a printer (not included) must be connected at first. Afterwards, the barometer must be connected via the serial port with a serial port of the computer. Finally, the control unit must be connected via the interface marked with “PC” to the computer. Once the BSS 2 shall be connected to the computer via Ethernet, only this cable has to be connected. In this case a direct connection has to be used between control unit and computer. The BSS 2 must not be part of a network. In order to enable the connection to the computer in the Windows network settings, the properties of the internet protocol version 4 (TCP/IPv4) must be set to “obtain address automatically”. The cables should be screwed in place rather than push-fit to ensure a good connection. 3.1.2.3 Safety circuit

The instrument can only be used when no person stands within its danger area. The range of beta radiation in air of Sr-90 is approximately 9 m. For this reason the BSS 2 is equipped with a safety circuit. Its assembly must be carried out in compliance with the national regulations and the requirements of the licence. One possibility, for instance, is a redundant design consisting of door contact and key-operated switch. This component is connected via the Sub-D connection on the rear panel of the control unit marked by „SECURITY INPUT“. The wiring of this plug is indicated in the attached data sheet. Operation without safety circuit is NOT possible. If modifications are carried out at the control unit or the connection, Eckert & Ziegler Nuclitec (EZN) does not undertake liability for any damages or malfunction of the device. The status of the safety circuit is indicated by a yellow light-emitting diode mounted on the control unit. If the diode is illuminated the safety circuit is broken and the shutter is closed. Once the safety circuit has been closed the shutter can be opened again.

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3.2 Software installation The software for operating the BSS 2 is already installed on the computer supplied with the instrument. It is installed in the BSS 2 directory on the hard disk (drive C:). A shortcut is defined on the desktop to the program Beta3240Xp.exe or Beta3240Win7.exe. The program is started by double-clicking on the icon. The "Power Save" function on the PC which is connected to the BSS 2 must be switched off. 3.3 Software operation Like all Windows programs, the software can be operated using the mouse or the keyboard. In the following text, menus and window elements are written in italics for clarity. Utilising the mouse, move the mouse arrow to the window element to be opened and confirm by pressing the left mouse key (click on the menu or the window element). The software can also be operated using the keyboard. In each point of the menu or window element there is a letter which is underlined. The window element is activated by pressing and holding down the „alt“ key and, subsequently, by pressing the key with the underlined letter of the desired window element. For selection of a sub-menu the „alt“ key must be held down until the desired window is opened. Example: For configuration of the computer port start from the start window and press the „alt“ key. By pressing the „C“ key, the configuration menu is marked. Hold down the „alt“ key. By again pressing the „C“ key the computer printer port menu is selected and the window for computer port configuration is opened. There is another possibility of using the keyboard to operate the software. With the „tab“ key you can move from one element of a window to the next one. Press the „enter“ key and the marked element is opened.

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3.4 Software configuration Before irradiations can be carried out with the BSS 2, the software must be configured. Select the configuration drop down menu from the start window. All parameters in the configuration menu must be set before the first irradiation can be started; from this the parameters „A / D - Converter“, „Humidity Sensor“, and „Sensor Adjustment“ are excluded as the sensors are adjusted prior delivery. However, they should be checked regularly, see sections 3.4.6 and 3.4.8.

Figure 13: Start Window with the Configuration Menu opened

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3.4.1 Language The language can be set to English or German via the language menu.

Figure 14: Start Window with the Language Menu opened

3.4.2 Decimal separators The decimal separator can be chosen to be a comma or a full stop (see figure 15). Press OK to save the selected separator or chose cancel to close the window without saving the selected separator. Please note that a warning message is displayed if a full stop is chosen, as the comma is recommended in ISO 31-0. The choice of separator has no effect on source data or Conversion coefficients. They must not be modified using another software.

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Figure 15: Selecting the Decimal Separator

3.4.3 Computer ports The communication between the BSS 2 and the computer is possible either via a standard printer port and a serial port or in the new version via a network interface (TCP/IP). The selection is shown in figure 16a. The configuration of the interfaces is described in the next two subsections.

Figure 16a: Selection of the computer port

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3.4.3.1 Printer and serial port

After selecting the computer port menu the submenu LPT/Ser. and then printer port has to be chosen, then the window shown in Figure 16b appears. As described in item 3.3, select the port to which the control unit should be connected using the radio button (in Figure 16, LPT1 has been selected). To save the selected port press OK. With cancel the window is closed without saving the selected port and the previous selection is retained.

Figure 16b: Selecting the Printer Port used

The BSS 2 is equipped with a sensor to measure the atmospheric pressure. The cable from the sensor is connected to a parallel port of the computer. Select the com port menu and the window shown in figure 16c appears. Select the port to which the sensor should be connected (in figure 16c COM 1 has been selected). To save the selected port press OK. With cancel the window is closed without saving the selected port and the previous selection is retained.

Figure 16c: Selection of the used serial port

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3.4.3.2 Network Interface

Figure 17 shows how to choose the network interface.

Figure 17: Selection of the network interface

3.4.4 Source Data Each source set is supplied with a CD-ROM which contains the calibration factors measured by the Physikalisch-Technische Bundesanstalt. To run the irradiation program these data must be copied onto the hard disk of the computer. These data are already installed on the computer if the irradiation unit is supplied.

Warning: The file with the source data must not be altered manually. The file is checksum protected – after a manual change the software will not start any more.

In the following it is described how to import additional source data, e.g. in order to use a second set of sources.

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Figure 20: Opening the Sources File

Select the sources data menu; the window shown in figure 20 will appear. Choose the CD-ROM drive and all the available files of type INI will be displayed. Select the file called quellen.ini and press OK. The window shown in figure 21 will then appear, showing a list of the radionuclides, the source set identifier and (to the right of the equals sign) the source number.

Figure 21: Existing Source Data

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Check that the source number matches the number on the back of the supplied source holders. Select “Add source data” to copy the information to the hard disc. A message “Data transmitted” will appear when the copying has been completed. If data are already stored on the hard disc, the data must be overwritten. A window will appear asking for confirmation that the data should be overwritten. Selecting “Cancel” will retain the old data on the hard disc.

Figure 22: Already Stored Source Data

3.4.5 Conversion coefficients The dose delivered to the dosimeter depends on the measurement conditions such as the phantom used and the angle of irradiation. Conversion coefficients for the different conditions must also be copied to the hard disk. These data are already installed on the computer if the irradiation unit is supplied.

Warning: The file with the conversion coefficients must not be altered manually. The file is checksum protected – after a manual change the software will not start.

In the following it is described how to import a new version which is distributed unregularly. The up to date version of the file is also available in the internet: www.ptb.de/en/org/6/63/f_u_e/BetaFakt.ini.

Select “Conversion coefficients” from the menu and the window shown in figure 23 will appear. As described in section 3.4.6, select the file BetaFakt.INI and confirm by pressing OK.

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Figure 23: Opening Conversion coefficients

Again, if the data are already stored on the hard drive, the program will prompt for confirmation that the data should be overwritten (Figure 24), however, only in case original file contains a newer version of the conversion coefficients.

Figure 24: Already Saved Conversion Coefficients

3.4.6 Analogue to digital converter

The A/D converter is calibrated prior delivery, however, it should be re-calibrated regularly (every 6 months), see section 5.3.2.1. 3.4.7 Angle sensor The dosimeter turntable incorporates a sensor to detect the angle of rotation. Before performing the first irradiation, the sensor has to be calibrated. The calibration is carried out at the limits of rotation (+90° and -90°). Select the angle sensor menu and the window shown in figure 18 appears. Set the turntable on BSS 2 to +90° and then press OK. The window shown in figure 19 appears. Now set the irradiation angle to -90° by again rotating the turntable of the BSS 2. Confirm by pressing OK.

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The sensor is now calibrated; this procedure does not need to be repeated unless any errors are detected.

Figure 18: Configuration of the Angle Sensor for Irradiation Angle +90°

Figure 19: Configuration of the Angle Sensor for Irradiation Angle -90°

3.4.8 Sensor Adjustment (Temperature, pressure, and humidity measurement) Sensors for pressure, temperature and humidity are supplied ready-calibrated. However, they should be adjusted regularly, see section 5.3.2. Once the sensors deliver wrong measurements, significantly wrong irradiations are the consequence for Pm-147:

1 K wrong temperature measurement results in a 2 % wrong dose(rate) 1 hPa wrong pressure measurement results in a 0.5 % wrong dose(rate) 10 % wrong realative air humidity results in a 0.5 % wrong dose(rate).

For the other nuclides the above listed wrong measurements result in less than 0.2 % wrong dose(rates).

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4 Operating the Beta Secondary Standard 2

4.1 Introduction 4.1.1 Source stand The dose rates from the sources have been determined at the source-dosimeter distances given in section 6.1. The source stand can be moved along the linear guiding and locked at the calibrated positions (11 cm, 20 cm, 30 cm and 50 cm). To move the source stand, pull the locking knob upwards (Figure 25) and hold it as the stand is moved along the guiding. At the required position, release the knob so that it returns to the end-stop; this ensures that the source is held at an accurately reproducible position.

Figure 25: Source stand with Locking Knob

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4.1.2 Turntable Dosimeters can be irradiated at angles ranging from -90º to +90º (in 5º steps) from the source-dosimeter axis. To change the irradiation angle, pull the locking knob upwards and hold it as the turntable is rotated to the required position. Release the knob so that the turntable locks into position. The turntable is equipped with a micrometer so that the reference point on the dosimeter can be placed accurately at the calibrated position (see section 4.2). The displacement is indicated on the digital display. To switch the micrometer on, press the left hand button; to zero the display press the right hand button. For further information on the micrometer, please refer to the manufacturer’s instruction manual.

On/off set to zero

Figure 26: Turntable with Displacement Device 4.1.3 Filter holder The beam flattening filters are mounted onto three rods and the filter card sensor on the source stand. Each filter is attached to a small identification card and three wires. To install the filter, first insert the identification card into the reader. Next, attach the hook opposite the card to the lower rod. Finally, attach the cross wires (the diameter of the eyelet matches the rod diameter to ensure that the filter is aligned correctly). Note that each eyelet must fit into the groove on the rod (figure 27).

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Figure 27: Filter Holding Device with Beam Flattening Filter

4.1.4 Installing a source holder The source holder must be installed after the instrument has been set up for the irradiation in order to reduce operator dose.

Figure 28: Source Holder Receptacle opened

The procedure for installing or removing the source must be completed without interruption. To install the source holder rotate the lever on the source support upwards (figure 28). Insert the source holder so that the guide pins on the source holder fit in the groove in hole in the source support.

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Push the source holder gently into the hole until the end-stop is reached. Rotate the lever downwards to lock the source into place (figure 29).

Figure 29: Source Holder Receptacle locked

To remove the source, rotate the lever upwards and pull the source holder out. Place the source holder in the transport container (or other suitable shielded store). 4.2 Positioning the dosimeter or phantom The dosimeter and phantom should be positioned so that the reference point of the dosimeter is directly above the axis of rotation of the turntable at a fixed distance from the source support. The plate mounted on the turntable must not be removed as it is exactly adjusted and mounted to the turntable. The specification of the adjust pin drills in the turntable is given in the Technical Data section. Together with the BSS 2 a rod phantom made of polymethylmethacrylate (PMMA) according to ISO is supplied.

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Figure 30: Positioning a dosimeter

X

X

B

Cbeam axis

beam axistu

rnta

ble

axis

probe reference point

probe reference point

distance rod

beam axis

A

distance rod

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To position the reference point of the dosimeter at the calibrated position, first move the source support to the 30cm source-detector distance and set the turntable to 0 degrees rotation. Remove the beam flattening filter (if fitted), and lock the distance rod into the opening for the source holder (see section 1.1.1). The tip of the distance rod is located above the centre of rotation of the turntable (figure 30 A).

Place the phantom and dosimeter in position on the table. Using the micrometer, adjust the position of the dosimeter so that the centre of the dosimeter touches the tip of the distance rod (figure 30B). Zero the micrometer using the (right hand?) button on the micrometer. Remove the distance rod from the source opening. Using the micrometer, move the turntable plate towards the source support so that the digital display on the micrometer displays the distance between the surface of the dosimeter and the reference point (figure 30C). This procedure ensures that the reference point is directly above the axis of rotation of the turntable and is at an accurately reproducible distance from the source for all source-dosimeter distances. Recommendation: The correct irradiation distance should be double checked using the distance rod before starting irradiation with different angels.

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4.3 Irradiation with the BSS 2 4.3.1 Record File Data on each irradiation are stored in a record file. To open the file, select the File drop down menu and choose record file. Enter the file name in the dialogue box or choose an existing file and press OK. The default file extension is .BTA. The options available are: New: generate a new record file Open: open an existing file, in which case the results are appended to this file. Print: print the current file Save: save the changes to the file Return to main menu 4.3.2 Irradiation Before an irradiation can start, the system must be initialised (already done by the manufacturer): Select the language (section 3.4.1) Select the decimal separators 3.4.2) Select computer port (section 3.4.3) Calibrate the analogue to digital converter (section 3.4.4) Calibrate the angle sensor (section 3.4.5) Enter the source data (section 3.4.6) Enter the conversion coefficients (section 3.4.7) Perform the sensor adjustment (calibration of the temperature, pressure, and

humidity measurement) (section 3.4.8) During irradiation no other programs must be running on the personal computer. In case the printer port is used the following is valid: The irradiation procedure may be disturbed if another program attempts to access the printer port or serial port.

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Figure 31: Irradiation Window

The irradiation can be performed indicating either the dose or the dose rate. Select the required type of irradiation in the irradiation menu (see figure 31). The program first displays the selected record file. (If no record file has been selected the message “open record file” appears (see section 4.3.1).) After closing the record file message, the irradiation menu is displayed. In case the conversion coefficients are too old, an error message occurs as shown below. In this case a newer file “BetaFakt.ini” must be chosen as described in section 3.4.7.

Select irradiation in the drop down menu (figureFehler! Verweisquelle konnte nicht gefunden werden. 31). The irradiation windows (figures 32 and 33) are very similar. They are divided into three columns:

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In the left column select (using the radio buttons) the dose or dose rate, the nuclide, the source-to-dosimeter distance and the type of phantom. The program does not accept inadmissible combinations of measurement parameters and phantoms. In the centre column enter the required dose (in the dose irradiation window only) and the irradiation angle. To save modifications of dose and irradiation angle, press the enter button or leave the field using the tab button or the mouse. Modified values are indicated in red, stored values are indicated in black. The fields for probe number or comments are for identification purposes only and do not have to be completed. Irradiation is operated via the start and stop buttons. Leave the irradiation window by pressing Exit. The centre column also shows the status of the shutter (“Open”, “Closed”, “No source” or “Error”). The right column shows the current settings of the instrument and the readings from the temperature, pressure and humidity gauges. The irradiation can start only if the settings match the parameters requested in the left hand and centre columns. Any parameters that do not match are indicated in red. For example, if the nuclide requested is Sr-90 but the Pm-147 source is positioned on the instrument, the Nuclide field will show Pm-147 highlighted in red. If the source is changed to Sr-90 the field will show Pm-147 and will change colour to grey. Once all the parameters are correct, the Start button will become live. Press the Start button to begin the irradiation. The status of the shutter and the source are indicated above the Start button (“Closed”, “Open”, “No source” or “Error”). The estimated irradiation time is shown in the top right hand corner of the window - due to certain approximations in the calculations the actual irradiation time may not match the estimated time exactly. The parameters in the window cannot be changed after irradiation has started. Irradiation can be stopped at any time during the period by pressing the Stop button. Irradiation can be restarted by pressing Start again. Any changes to the instrument settings will automatically stop the irradiation. The irradiation will also be terminated if the safety circuit is broken; in this case it is not possible to restart the irradiation.

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Operation Manual


4.3.2.1 Irradiation with dose indication

Figure 32: Start Window indicating the dose

If the irradiation is performed to obtain a preselected dose, the dose and the corresponding uncertainty are indicated in the upper box. The uncertainty is determined according to “ISO Guide to the Expression of Uncertainty in Measurement” with a coverage factor of k = 2 (corresponding to a level of confidence of approximately 95 %). The uncertainty takes into account the source calibration, the sensor readings (based on manufacturers’ data) and the calculated shutter opening and closing times. In the display for the irradiation time two values are indicated. The first value shows the actual time of irradiation, the second value shows the estimated time of irradiation. The estimated irradiation time is included to allow measurements to be planned; the actual irradiation time taken may differ slightly from this figure. The irradiation stops automatically when the preselected dose is reached. The irradiation can be stopped at any time by pressing Stop. Also in such a case the irradiation including the dose is recorded.

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Operation Manual


4.3.2.2 Irradiation with dose rate indication

Figure 33: Start Window indicating the dose rate

If an irradiation is performed with the dose rate indicated, both the current dose rate and the corresponding uncertainty are indicated in the upper box. The uncertainty is determined according to “ISO Guide to the Expression of Uncertainty in Measurement” with a coverage factor of k = 2 (corresponding to a level of confidence of approximately 95 %). The uncertainty takes into account the source calibration and the sensor readings (based on manufacturers’ data). Shutter opening and closing times are not considered. Before the irradiation starts, the dose rate and the uncertainty are indicated in grey for planning purposes. In addition to the dose rate, the irradiation time is indicated and stored in the record file. It does not influence the irradiation. During the irradiation information can be entered in the comments field which is also stored in the record file. The irradiation can be stopped at any time by pressing Stop.

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Operation Manual


5 Quality control

5.1 To test the sensors After selection of the test menu the window shown in figure 34 is visible. The window displays the current measured uncorrected temperature, humidity, angle, uncorrected pressure, and the test voltage at the test input (JP7 or BNC depending on whether an old or new control unit is in use) of the BSS 2. The addition “uncorrected” means that the sensor adjustment described in section 5.3.2 is not taken into account. However, that sensor adjustment is taken into account for the display of the temperature and air pressure in the window for irradiations, see section 4.3 and for the determination of the dose(rate).

Figure 34: Test Display

The window also controls the calibration of the sensors (see sections 5.3.2.2 to 5.3.2.4) and the calibration of the analogue to digital Convertor (section 5.3.2.1). The unit used to display the atmospheric pressure or can be changed by selecting “Change range”. 5.2 Shutter test The source shutter can be opened or closed by selecting “open shutter” or “close shutter”, see figure 34, in the test menu for testing the mechanical operation. An error message will be displayed if the system detects a problem.

BSS-2

Operation Manual


5.3 Calibration 5.3.1 Source calibration The sources used by the BSS 2 are calibrated before delivery, and the software takes into account the half-life. It is normally not necessary to recalibrate the sources during their 10 year recommended working life. Sources are calibrated with their matching beam flattening filter. If the filter has to be replaced, the source / filter pair must be recalibrated. 5.3.2 Sensor Adjustment (temperature, pressure, and humidity measurement) 5.3.2.1 Analogue to digital convertor calibration

The analogue to digital convertor (ADC) should be checked every six months. Warning: The adjustment of the ADC affects the results of the temperature and humidity measurements. If the ADC is calibrated, afterwards the measurements of the temperature and the humidity must be checked, too (see 5.3.2.3 and 5.3.2.4). The power source used must have an absolute accuracy of at least 1 mV, otherwise the correctness of the measurements performed with the BSS cannot be guaranteed.

Switch the BSS 2 on and allow it to warm up for about 30 minutes.

Only for devices with parallel and serial port (old devices): Loosen the two bolts on the rear panel of the control unit and remove the casing by lifting it backwards (see Figure 35).

Figure 35: Rear Panel of the Control Unit

Note: There is a risk of touching live electrical components during this procedure. This adjustment should be carried out by appropriately trained and experienced staff only Plug the supplied test cable into Jumper 7 (JP7) on the control board (the left hand circuit board when viewed from the front of the control unit (see figure 36). Connect the BNC plug on the test cable to a calibrated power source. The maximum input voltage of the analogue to digital convertor is + 5 V.

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Operation Manual


Jumper JP7 Poti P1 Poti P2

Figure 36: Control Unit with its Casing opened

Open the test window (section 5.1) to display the measured test voltage. Set the applied voltage to + 100.0 mV. Adjust potentiometer P1 so that the voltage displayed equals the applied voltage (this adjustment sets the offset). Change the applied voltage to + 4.9000 V and adjust potentiometer P2 so that the voltage displayed equals the applied voltage (this adjustment sets the gain). Set the voltage back to + 100.0 mV and check the displayed voltage; adjust P1 if necessary. Change the voltage to + 4.9000 V and adjust P2 again if necessary. Repeat the procedure until no further adjustment is needed. To finalise the configuration of the software the step “Configuration of the A/D converter” described below must be performed. Only for devices with Ethernet port (new devices): A test input is located at the backside of the control unit, see figure 12b on page 12, which must be connected with a calibrated power source via a BNC cable. For all devices in case software version 4.0 or higher is used: Configuration of the A/D converter: Via the menu Configuration - A/D converter - Calibrate the calibration of the A/D converter is started, then the following window is shown:

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Operation Manual


To adjust the offset a voltage of 0.1000 V must be chosen with the calibrated power source, this must be confirmed by choosing “OK”. Then, the measured voltage is shown and can be confirmed via “Next”.

Then the user is asked to apply a voltage of 4.9000 V.

After applying this voltage “Ok” has to be chosen.

Again the measured voltage is shown and can be confirmed via “Next”. Finally, the window closes and the calibration is finished. 5.3.2.2 Atmospheric pressure

The atmospheric pressure sensor contained in the control unit of the BSS 2 must be compared annually with an independent instrument that is traceable to a national or international standard.

To display the atmospheric pressure measured by the BSS 2, select the test menu (see section 5.1). Compare the displayed result to the pressure shown on the independent instrument. If the two readings differ by more than 0.1 % the calibration of the sensor must be adjusted.

BSS-2

Operation Manual


The calibration included in the BSS 2 software assumes a linear relationship between the actual and measured atmospheric pressure over the range 80 kPa to 110 kPa:

actual air pressure = air pressure indicated * gain + offset

The values of the gain factor and the offset (the latter in units of kPa) can be edited under sensor adjustment in the configuration menu.

The adjusted values are used by the software for irradiations. However, in the test menu the values of the pressure remain unaffected. 5.3.2.3 Temperature

The temperature sensor must be compared annually with an independent instrument that is traceable to a national or international standard.

To display the temperature measured by the BSS 2, select the test menu (see item 5.1). Compare the displayed result to the temperature shown on the independent instrument. If the two readings differ by more than 0.25 °C the calibration of the sensor must be adjusted.

The calibration included in the BSS 2 software assumes a linear relationship between the actual and measured temperature (in units of °C):

actual temperature = temperature indicated * gain + offset

The values of the gain factor and the offset (the latter in units of °C) can be edited under sensor adjustment in the configuration menu. The adjusted values are used by the software for irradiations. However, in the test menu the values of the temperature remain unaffected. 5.3.2.4 Humidity

The hygrometer used by the BSS 2 must be checked at least once a year. For this check humidity standards for the production of a relative air humidity of 35 % and 80 % from the hygrometer’s manufacturer (http://www.rotronic.com/eaxx-scs.html?___store=english) shall be used. The calibration can be done via Humidity Sensor – Calibrate in the menue Configuration, see figure 37. The window shown in figure 38 appears. Once the humidity sensor is exposed to a reference

BSS-2

Operation Manual


humidity of 35 % the calibration can be started via „Ok“. As soon as the humidity is stable the button „Next“ can be chosen. The stabilization process can take up to one hour. After choosing „Next“ the window shown in figure 39 appears. Once the humidity sensor is exposed to a reference humidity of 80 % the calibration can be continued with „Ok“. Finally choosing „Next“ finishes the calibration (this may also take up to one hour). The adjusted values are used by the software for irradiations. However, in the test menu the values of the humidity remain unaffected.

Figure 37: Menu to calibrate the humidity sensor

Figure 38: Window to start the calibration of the humidity sensor at 35 % humidity

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Operation Manual


Figure 39: Window to calibrate the humidity sensor at 80 % humidity

5.4 Maintenance There is no maintenance work necessary, except see under section 5.3.2. 5.5 Malfunctions 5.5.1 Failure of the shutter The shutter position is indicated in the centre column of the irradiation window. The conditions are: open, closed, no source and error. If the program indicates an error with the shutter, press the Stop button to try to close the shutter. If this is not successful, try to close the shutter via close shutter in the test menu. If the shutter does not close under computer control, the following procedure may be used by suitably qualified and experienced staff. The source holder must be placed in the transport container as soon as it is removed from the source support. 1. If the shutter of the source holder cannot be closed with the BSS 2 software, check

whether the source holder can be removed.

2. If the source holder cannot be removed, the shutter can be closed using a long

screwdriver or rod. Throughout the operation, stand behind the source stand to keep the dose as low as possible.

3. If the shutter can still not be closed, the shutter should be removed from the

source holder. For this remove the snap ring using the supplied pincers (figure 40) and remove the shutter. By now the source is unshielded. The source holder can then be removed from the source support. Place the source in the transport container, taking care not to point the open face of the source towards any staff.

BSS-2

Operation Manual


snap ring which has to be removed Figure 40: Source Holder

5.5.2 Shutter cannot be opened If the shutter cannot be opened, check that: The cables have been connected correctly The safety circuit has been connected correctly 5.5.3 Communication with the atmospheric pressure sensor is interrupted Communication with the atmospheric pressure sensor is interrupted is indicated when the software tries to communicate with the atmospheric pressure sensor but no readings are received. Two possible causes are: - Incorrect cable connections - The sensor is carrying out a self-test procedure (this procedure runs for about

1 minute after the sensor is switched on). 5.6 Sources exchange Replacement sources are available from the supplier.

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Operation Manual


6 Technical data

6.1 Specification of beta sources, beam flattening filters and calibration distances

Calibrations at other combinations of distance and filter are possible on request at PTB. The manufacture of Ru-106/Rh-106 is planned for the future.

Parameters Specification of the Parameters

Radionuclide 147Pm 85Kr 90Sr/90Y 106Ru/106Rh

Source type EZN PHRB4809

EZN KARB4810

EZN SIRB4568

EZN

Nominal activity 3.7 GBq 3.7 GBq 460 MBq 20 MBq

Superficial density of source window

(2.22 0.5) mg/cm2 titanium

(11.3 1.1) mg/cm2 titanium

(79 8) mg/cm2 stainless steel

(105 ± 10) mg/cm² Silber

Filter material Hostaphane - Hostaphane

Dimensioning of the beam flattening filters mounted at 10 cm distance from the source

1 circular foil, 5 cm in radius

and 100 µm thick with one hole, 0.975 cm in

radius, in the centre

1 circular foil 4 cm in radius

and 50 µm thick,

and 1 foil, 2.75 cm in radius and 190 µm

thick

3 concentric circular foils

190 µm thick. 2 cm, 3 cm

and 5 cm in radius

- as for 90Sr/90Y or

without

Mean beta energy

0.06 MeV 0.24 MeV 0.8 MeV 1.2 MeV

Nominal value of the absorbed dose rate

)(0,07;0g D in 0.07 mm tissue at the calibrated distance

3 µSv/s at 20 cm

50 µSv/s at 30 cm

10 µSv/s at 30 cm

120 µSv/s at 11 cm;

35 µSv/s at 20 cm;

15 µSv/s at 30 cm;

6 µSv/s at 50 cm

8 µSv/s at 11 cm

(w/o filter);0,7 µSv/sat 30 cm

(with filter)

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Operation Manual


6.2 Safety circuit Assignment of the 15 pole Sub-D connection

Pin number of the Sub-D plugs

Signal Identification in Figure 38

1 and 2 relay point 1 break A

3 and 4 relay point 1 combined B

5 and 6 relay point 1 make contact C

7 door contact make contact X

8 --- ---

9 and 10 relay point 2 break D

11 and 12 relay point 2 combined E

13 and 14 relay point 2 make contact F

15 door contact make contact Y

Figure 38: Contacts of the Safety Circuit Relay contacts represented with locking closed. Door contact represented with door open.

Relay contacts 48 V/1 A

Door contact

BA D

E

FC

X Y

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6.3 Turntable plate The dosimeter and phantom should be positioned so that the reference point of the dosimeter is directly above the axis of rotation of the turntable at a fixed distance from the source support.

BSS-2

Operation Manual


6.4 Loading capacity of the turntable The load applied to the turntable must not exceed 100 N. The maximum torque around the three axis on the table plate must not exceed 6 Nm. 6.5 Cable lengths

Connection Cable length

computer (printer port) - control unit 2 m

computer (serial port) - control unit (atmospheric pressure sensor)

2 m

control unit - printer 2 m

control unit - irradiation device 5 m

control unit - temperature and humidity sensor 5 m

control unit - safety circuit 5 m

6.6 Supply voltage The control unit will be factory set for the mains power supply of the country to which the instrument is delivered (see 3.1.2.1).

range A: 220 V - 240 V range B: 110 V - 115 V

Documents

Operation Manual Beta-Secondary Standard 2 (BSS-2)...“interface” is illuminated when the BSS 2 is controlled by the computer. The control unit also includes additional independent