3. PHANTOM QUALIFICATIONA sample of 8 phantoms has been included in a characterizationstudy. The phantoms were located on an irradiation test fixtures andpresented to a 10 MeV electron beam at the Mediscan irradiationfacility at Kremsmünster, Austria in such a way that the electronbeam was hitting the phantoms perpendicularly. Doses of thealanine dosimeters were measured with a Bruker escan EPRspectrometer, the radiochromic films with a Hitachi U-5100 spectro-photometer. The PMMA dosimeters were not included in this study.The applied dose was in the order of 17 kGy.The temperature distribution was measured using a calibratedTest 880-3 thermo camera. Fig. 2 shows the temperature distribu-

tion on the left side together with the optical image on the rightside for comparison. The absorbed dose was again 17 kGy.

Fig. 2 Thermal and optical image of the irradiation phantom

5. CONCLUSIONA novel irradiation phantom was designed and characterized for a10 MeV E-Beam. The phantom can house several dosimeter typesand is easy to handle. The spread in measured doses was found tobe below 1% for alanine dosimerts and below 2 % for radiochromicfilm dosimeters (at 1σ). The temperature distribution in the phan-tom shows a good uniformity, so the different dosimeters face thesame temperature within a few degrees centigrade.

4. RESULTSThe following table shows the coefficients of variation (CV) in per-cent for 8 alanine pellets, 10 alanine films and 5 FWT- 60 films inphantoms P1 to P8, together with the average CV over all phan-toms.

The difference between the average measured dose of the alaninepellets and alanine film was 3.1%, the difference between alaninefilms and FWT dosimeters 1.4 %, respectively. This difference canbe partly traced to different calibration curves used.The phantom was used in a calibration exercise where FWT- 60films were irradiated together with alanine film dosimeters. Theaverage variation coefficient of FWT- 60 response over 14 runs andmeasurement with 2 different spectrophotometers (at wavelengths510 and 605 nm) was 1.5 %.

A Novel Irradiation Phantom for E-Beam ProcessingD. Hanis, B. Kaiblinger, J. Mittendorfer, M. NiederreiterMediscan GmbH & Co KG, Bad Haller Straße 34, A-4550 Kremsmünster, Austria

ABSTRACTThis paper presents a novel irradiation phantom for high energy(10 MeV) E-beam processing. The phantom is primarily designedfor dosimeter calibration, but other applications where a definedirradiation configuration is desired are feasible.

The phantom is made of polyamide and houses compartmentsfor alanine pellets, alanine films, radiochrome films and PMMAdosimeters. The compartments are designed to guarantee equalirradiation conditions for each dosimeter type.

1. INTRODUCTIONIn several applications of radiation processing there is a need fora well defined irradiation geometry and very stable irradiation con-ditions. One example is In-situ/In-Plant calibration using routinedosimetry systems in a production irradiator using a transfer stand-ard dosimetry system. This procedure is described in detail in theapplicable standard ISO/ASTM 51261 “Standard Practice for Cali-bration of Routine Dosimetry Systems for Radiation Processing” [1].Routine and transfer dosimeters are co-located in an irradiationphantom in such a way that both dosimeter types receive the sameabsorbed dose.

ISO/ASTM 51261 describes in appendix A1 an example for a10 MeV energy electron beam phantom which is widely used inindustry. The described phantom can house radiochromic filmdosimeter together with alanine pellets.

With the increasing use of Alanin film dosimeters this phantombecomes a little inconvenient when alanine films have to be co-located with alanine pellets. For this reason a new phantom hasbeen developed which can house alanine film dosimeters, radio-chromic films, alanine pellets and PMMA dosimeters.

2. PHANTOM DESIGNFig. 1 shows the irradiation phantom which consists of a base anda cover plate, both made of Polyamid PA 66.

Distinct locations for 4 dosimeter types are present. The phantomcan be loaded with:• 8 alanine pellets in 2 holders (from Riso Lab)• 10 alanine films (Kodak BioMax)• Appr. 5 – 8 radiochromic film dosimeters• PMMA dosimeters (Red Perspex 4043)

The principal requirement for a calibration phantom is that alldosimeter receive the same absorbed dose. One aspect of thisrequirement is that the center of each dosimeter is on the samelocation of the depth-dose curve, independent of the dosimetergeometry. The PP-66 depth dose curve used for the design wascalculated using the Monte Carlo code ITS3 [2]. The surface doseuniformity has been qualified to be less than 1.5 % on the phan-tom surface area. Fig. 1 Irradiation Phantom Layout

Mediscan GmbH & Co KGBad Haller Straße 34, A-4550 KremsmünsterAustria

Dosimeter Type P 1 P 2 P 3 P 4 P 5 P 6 P 7 P 8 Avg. CV [%]

Alanin Pellets 0,76 0,43 1,81 0,42 1,36 0,62 0,31 0,90 0,83

Alanin Films 0,87 0,97 0,84 1,15 1,35 0,92 0,88 1,24 1,03

FWT- 60 Films 0,87 1,44 0,66 5,78 1,02 1,33 1,10 1,18 1,67

References[1] ISO/ASTM 51261 “Practice for calibration of routine dosimetry systems for radiation

processing”, ASTM, 100 Barr Harbor Dr., Conshohocken, PA 19428.[2] HALBLEIB, J. A., et al., “ITS Version 3: The Integrated TIGER Series of Coupled Electron/

Photon Monte Carlo Transport Codes”, SAND91-1634 (March 1992)

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