U N I V E R S I T Y

L a f a y e t t e

OF

LOUISIANA

RockSat 2010Team CajunSat

Mark RobertsDr. Andy Hollerman

Department of PhysicsUniversity of Louisiana at Lafayette

Lafayette, Louisiana 70504

June 23, 2010

• Graduate student Mark Roberts decided to design and build an improved Geiger counter from the component that could detect cosmic rays from high altitude or near Earth space.

• We decided to participate in both the LASPACE HASP 2009 and RockSat programs for this payload.

• Mark will use his work on these projects for his Master’s degree research.

RockSat Objectives

Functional Block DiagramFunctional Block Diagram

AVRMicrocontrollerZ

Accelerometer

X/YAccelerometer

Temperature & Pressure Sensor

GPS

Geiger Circuit

G-switch

Flash Memory

RBF

Power Sub-

system

Temperature PCB

Port Sensors

BatteriesLithium 9 Volt

AVRPCB

PowerData

Systems Layout: Electronics PlateSystems Layout: Electronics Plate

Micro-controller

BatteriesGeiger Counter

OSL Badge

GPS

TempPCB

OSL Badge G-Switch

Z Accelerometer

Subsystems LayoutSubsystems Layout

Micro Controller BoardMicro Controller Board

Geiger-Mueller Geiger-Mueller TubesTubes

LND 7134LND 72118

Dead Time (µs) 70LND 72118

Gamma Sensitivity

(CPS/MR/HR)45

Tube Capacitance (pF)

3

Dead Time (µs) 45Gamma

Sensitivity (CPS/MR/HR)

7.5

Tube Capacitance (pF)

3

LND 7134

8

What is Dead Time?What is Dead Time?

Dead Time : The minimum time between detectable pulses will be less than the recovery Dead Time : The minimum time between detectable pulses will be less than the recovery time. This is the pulse resolving time.time. This is the pulse resolving time.

Non-paralyzable dead-time: is defined as an event that occurs during this period is not Non-paralyzable dead-time: is defined as an event that occurs during this period is not counted nor does it influence the ability of the tube to respond to later events.counted nor does it influence the ability of the tube to respond to later events.

Paralyzable dead time (resolve time): is the time duration between the end of the non-Paralyzable dead time (resolve time): is the time duration between the end of the non-paralyzable dead time and a resolving point at which a pulse larger than the discriminator paralyzable dead time and a resolving point at which a pulse larger than the discriminator level can be developed.level can be developed.

Split Source Method to determine Dead Time Split Source Method to determine Dead Time

A split radiation source is nothing more than a radioactive source that is split into A split radiation source is nothing more than a radioactive source that is split into two pieces.two pieces.

The source as a hole is considered to be the combined sources of NThe source as a hole is considered to be the combined sources of N11 and N and N22 therefore I will call it Ntherefore I will call it NCC . N . N1 1 is the left side of the split source for me; making Nis the left side of the split source for me; making N2 2

the right side of Nthe right side of NCC..

Counts are taken from NCounts are taken from N11,, NN22, and, and NNC C sources with the same time duration. Then sources with the same time duration. Then the dead time of the system can be calculated by the dead time of the system can be calculated by

1 2

1 22CN N N

TN N

[seconds]

I made my own split source with some Uranyl Acetate I made my own split source with some Uranyl Acetate that was laying around which happens to contain that was laying around which happens to contain Uranium 238! =o)Uranium 238! =o)

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Geiger PlateausGeiger Plateaus

11

Geiger CounterGeiger Counter

Geiger CounterGeiger Counter

-3.2 -2.1 -1 0.1 1.2 2.3 3.4 4.5 5.6 6.7 7.8 8.9 10 11.1 12x 10-4

450

500

550

600

650

700

750

800

850

900

Time (sec)

Volta

ge (V

)

Structure SubsystemStructure Subsystem

We have already milled the platforms. Also all structure We have already milled the platforms. Also all structure hardware (standoffs, bolts/nuts) has been received.hardware (standoffs, bolts/nuts) has been received.

Air tight chamber for static portAir tight chamber for static port

Also have Polyethylene Also have Polyethylene tubing (1/4’’ x .170’’ x 25 ft) tubing (1/4’’ x .170’’ x 25 ft) fitted with a ¼’’ OD x ¼” NPT fitted with a ¼’’ OD x ¼” NPT connector.connector.

The Stay Puft TestThe Stay Puft TestThe average off the shelf Marshmallow is a foam object with The average off the shelf Marshmallow is a foam object with closed wall air cells within the foam. closed wall air cells within the foam. By placing a Marshmallow in a Vacuum the walls will expand By placing a Marshmallow in a Vacuum the walls will expand with reduction of pressure; when air is allowed back into the with reduction of pressure; when air is allowed back into the chamber the walls collapse hence the marshmallow rapidly chamber the walls collapse hence the marshmallow rapidly deflates to a shriveled state from it’s original form.deflates to a shriveled state from it’s original form.

The Stay Puft Test is to demonstrate the effectiveness of the air tight The Stay Puft Test is to demonstrate the effectiveness of the air tight containers' constructed. One marshmallow is placed inside the air tight containers' constructed. One marshmallow is placed inside the air tight container and then placed into the vacuum chamber along with another container and then placed into the vacuum chamber along with another marshmallow.marshmallow.

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Other Tests performed…Other Tests performed…

Shock/Stress Testing

Heat TestCold Test

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Integrated PayloadIntegrated Payload

Conclusions• Launch the RockSat Geiger counter payload on June 24,

2010 at the NASA WFF.

• Continue working with students to develop payloads for high altitude balloons and rockets:

- Recruit new outstanding graduate and undergraduate students (available $17.5k/yr Master’s degree fellowship).

• Begin outreach into the physics and engineering of rocket flight to local K-12 schools.

• Write winning proposals to continue efforts into the future:

- NASA EPSCoR Louisiana State Submission - Spring 2010 (subcontractor to Louisiana Tech University - $115k/yr).

• Continue training students with the motto “walk before you run...”.

Acknowledgements

• Drs. Greg Guzik and John Wefel at Louisiana State University for all their help in the development of our LaACES and HASP payloads.

• Other travel and related funding was provided by the State of Louisiana Board of Regents using the Space Grant Program.

• Colorado Space Grant and RockSat for providing this oppurtunity.

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Questions???Questions???