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Measurement of energy spectra of α particles by a solid state detector

A primer course of experimental particle and nuclear physics. Measurement of energy spectra of α particles by a solid state detector. Pham Tuan Anh Osaka, March 6 th 2009. Purpose of experiment. Measurement of energy spectra of α- particle Determine resolution of solid state detector

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Measurement of energy spectra of α particles by a solid state detector

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  1. A primer course of experimental particle and nuclear physics Measurement of energy spectra of α particles by a solid state detector Pham Tuan Anh Osaka, March 6th 2009

  2. Purpose of experiment Measurement of energy spectra of α- particle Determine resolution of solid state detector 241AmSource: Solid state detector: Si 241Am 5/2- 9/2- 5388.0 keV (1.4%) 7/2- 5442.9 keV (12.8%) 5/2- 5485.6 keV (85.2%) 5/2+ 237Np

  3. Operation of Si detector P- region N- region + V Depletion region Picture source: www.qsl.net/k0ff/5usPulse.jpg

  4. Collected charged Q Q = η.e.(Eloss/E0) Outputted pulse – height ~ Q E0 = 3.5 eV  high resolution detector

  5. Configuration in the vacuum chamber Si detector Collimator Al foil Am241

  6. The vacuum chamber Valve 3 Pressure gauge Vacuum chamber Valve 1 Valve 2 Rotary pump Vacuum chamber: ~ 0 cm Hg

  7. Configuration of measurement systems • Voltage setup : 100 V • Time for each measurement: 2 minutes. MCA Computer Si α-incident Pre-amplifier Amplifier + V

  8. Vacuum chamber

  9. Rotary pump

  10. Pre-Amplifier

  11. Amplifier & MCA

  12. Computer

  13. System measurement

  14. Process • 1. Turn on supply: set voltage 100 V (warm-up time ~ 20 minutes). • 2. Close valve 1, 2 and 3. • 3. Turn on rotary pump. • 3. Open valve 2 slowly and look at pressure gauge. (76 cm Hg indicator0 cm Hg inside chamber) .

  15. Process • 4. Turn on computer and look at MCA program. • 5. Set time of measurement. • 6. Energy calibration of the Si detector. • 7. Measurement of energy loss of α particles in materials. • 8. Determination of Al thickness. • 9. Determination of resolution of detector.

  16. Result 2. Measurement of energy loss of α particles in materials

  17. Thank you for your attention

  18. Thank you for your attention

  19. Answer questions • Question 12: • N_(e+p) = E/E_0 ~ 1.56E6 • Expected resolution: • R = 2.35/σ = 2.35/√N = 0.19% • R = 2.35.√(FE_0/E) = 0.07% (F: Fano factor) • Out experimental experiment • R = FWHM/E = 1.82%

  20. Answer questions • FWHM = 2.35/σ = 2.35/√N • Increasing E  FWHM decrease  R decrease  High resolution • R = FWHM/E ~ 1/N1/2

  21. Bibliography Source: • 1. http://www.qsl.net/k0ff/5usPulse.jpg

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