TEST OF BC400 SCINTILLATOR RESPONSE TO GAMMA AND BETA SOURCES

1PAUL SCHERRER INSTITUT

TEST OF BC400 SCINTILLATOR RESPONSE TO GAMMA AND BETA SOURCES

Kick-off, 4 Apr 2007

W. Hajdas, E. Suarez-Garcia, K. Egli, A. Mtchedlishvili

PSI, Villigen, CH


Scintillators


• 70 BC400 bars (5.8x5.8x200) delivered from St.Gobain

• Unit price 54 US$, delivery time 2.5 months

• Very good quality and small STD for dimension differences

• Teflon and Alu coating as well as no coating tests of linearity

• Surface quality test with Profile-meter from NanoLab (see Estela talk)

• Two pieces to IBJ(PL) for polishing and tests (see Radek talk)


Scintillators


Teflon and Alu Coated BC400 plastic scintillators (5.8x5.8x200 mm3)


Readout Electronics


BC400 Plastic

H8500MAPMT

High Voltage

X10 Fast Amplifier

Delay

Fast Discriminator

Linear Integrator

PC +MCA

Gate


Readout Electronics



Test Setup


‘Dark chamber’ with 64 outputsand HV input

H8500 MAPMT with rails for source handler


Scintillator and Source Mounting


Single BC400 arranged on H8500(optical fat coupling)

Source leather mount on the rail in front of BC400


Scintillator and Source Mounting


Source in holder on top;chamber view from above

Source in the middle position on the leather


Measurements


• Runs with following sources:90Sr (beta) 241Am (gamma, 60 keV)57Co (gamma, 122 keV)

• Positions along scintillator bar: low (close to PM), middle, high

• Measurement: Beta-spectrum maximum position Compton edge (ev. with Photopeak) extrapolated range

• Coating for BC400:Al (2), Teflon (2) and no Coating

• Two Anodes:Nr 64 and Nr 8)

•High VoltageV= 1000 V and 1050 V


Spectra – 90Sr and 241Am



Spectra – Signal and Background



Spectra – Low and High Source Location



Method I - Maximum



Method II - Extrapolation



Results 90Sr, Al and Teflon Coating, 4 bars

90Sr Test of Max, Alu Coating

0

50

100

150

200

250

300

350

400

Al-1 L Al-1 M Al-1 Hi Al-2 L Al-2 M Al-2 H


90Sr Test of Max, Teflon Coating

0

50

100

150

200

250

300

350

Tf-1 L Tf-1 M Tf-1 H Tf-2 L Tf-2 M Tf-2 H


Results 90Sr, No Coating and Anode Nr 8

90Sr Test of Max, No Coating

0

50

100

150

200

250

300

350

400

No C. L No C. H


90Sr Test of Max, Al Coat, Anode Nr 8

0

100

200

300

400

500

600

Al-P8 L Al-P8 H


Results 241Am, Al and Teflon Coating, 4 bars

241Am Test of Edge, Al Coating

0

20

40

60

80

100

120

140

Al-1 L Al-1 H Al-2 L Al-2 H


241Am Test of Edge, Teflon Coating

0

20

40

60

80

100

120

140

Tf-1 L Tf-1 H Tf-2 L Tf-2 H


Results 241Am HV and 57Co

57Co Test of Edge, Al Coating

0

20

40

60

80

100

Al-2 L Al-2 H


241AM Test of Edge, Al Coating, HV=1050

0

20

40

60

80

100

120

140

160

180

Al-2 L Al-2 H


Results Summary


• Mean High vs. Low Shift for Al = 10% (results from both Sr, Am sources)

• Mean High vs. Low Shift for Teflon = 10%

• Mean High vs. Low Shift for no Coating = 18% (results from 1 bar only)

• Mean Middle vs. Low Shift for Al+Teflon = 2%

• Mean Shift from 90Sr source = 8%

• Mean Shift from 241Am+57Co sources = 15%

• (single worst result for one data point = 43%, Chi2 = 2.)


Conclusions


• Coating thickness for beta and background for gamma – error sources

• Light Output reduction along BC400 bar is small (10%)

• Data confirms Monte Carlo results with Optical Photons

• Polishing quality of BC400 from factory is already satisfactory

• No need for wavelength shifters

• Trade: further polishing vs. bar width distribution straggling


Extra: Test with Big Plastic and 90Sr



Extra: Max Shift in Al Foils for 90Sr


TEST OF BC400 SCINTILLATOR RESPONSE TO GAMMA AND BETA SOURCES

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