Scientific Measurements with ACS-EM: Results and Spectrum Analysis

1. SPI - ACS EM Scientific Measurements August 19 - September 4, 1998 at DSS (Friedrichshafen) A. v. Kienlin, R. Georgii, C. Wunderer SPI-Team Meeting, Paris, 7.-9.10.98

2. Overview • ACS EM configuration for scientific measurements • Results • Linearity and Calibration of Energy and Event Thresholds • Single Photoelectron Spectrum • Gamma-ray Line Spectra • Processing Times and Jitter • Overrange Signals, overall ACS rate monitor (“burst mode”) • Problems encountered • SPI Documents: SPI-MPE-PL-12-22 (Plan) SPI-MPE-RP-12-26 (Report, in preparation) SPI-Team Meeting, Paris, 7.-9.10.98

3. ACS EM SPI-Team Meeting, Paris, 7.-9.10.98

4. U Q ACS EM Configuration for scientific measurements (I) • 1 BGO detector module • 2 PMTs • 1 BGO crystal, consisting of 2 crystal blocks glued together, total dimensions 1.6  5  8 cm3 • 1 LED dummy • 2 PMTs • 3 LEDs for generation of single photoelectrons (SPE), lower energy and overrange events • 1 RC circuit (“charge box”) for precise charge injection to CSA input of FEE C R SPI-Team Meeting, Paris, 7.-9.10.98

5. LED-Dummy SPI-Team Meeting, Paris, 7.-9.10.98

6. BGO Crystal Detector Module SPI-Team Meeting, Paris, 7.-9.10.98

7. ACS EM Configuration for scientific measurements (II) • 1 FEE with CSA output connector (“reference FEE”)(not officially part of ACS EM) • FEE Unit Tester (FEE-UT) • 2 FEEs • EMC representative ACS EM with VCU • VCU Unit Tester (VCU-UT) • all 3 FEEs: design status MARCH 1998 SPI-Team Meeting, Paris, 7.-9.10.98

8. FEE-Unit Tester with FEE and LED-Dummy SPI-Team Meeting, Paris, 7.-9.10.98

9. VCU - Unit Tester SPI-Team Meeting, Paris, 7.-9.10.98

10. Linearity of Event-Trigger Thresholds SPI-Team Meeting, Paris, 7.-9.10.98

11. Linearity of Energy Thresholds SPI-Team Meeting, Paris, 7.-9.10.98

12. Generation of Differential Spectra • Measure number of counts per 5 sec for each energy or event-trigger threshold setting • This „Stepping Method“ yields integral energy spectra (counts above threshold) • Differentiate to obtain energy spectra (counts per channel) SPI-Team Meeting, Paris, 7.-9.10.98

13. Single Photoelectron (SPE) Spectrumusing LED Dummy PMT : HV nominal (1129 V) HV low (1088 V) HV high (1170 V) SPI-Team Meeting, Paris, 7.-9.10.98

14. Single Photoelectron Measurements • Using • FEE event-trigger threshold calibration (knowledge of charge at CSA input corresponding to an event-trigger level) • knowledge of PMT gains at different HVs • observed peaks correspond to 1.7 x 10-19 ( 0.3 x 10-19) Cb generated at photocathode • SPE spectrum from LED with a different FEE corresponds to 2.0x10-19 ( 0.3 x10-19) Cb • results consistent with expected values (single photoelectrons!)!! So far SPEs measured only using LED Dummy !! SPI-Team Meeting, Paris, 7.-9.10.98

15. Ab hier „Reservefolien“ SPI-Team Meeting, Paris, 7.-9.10.98

16. Detail ACS EMLED-Dummy and „Crystal Dummy“ SPI-Team Meeting, Paris, 7.-9.10.98

17. LED - SPE Spectrum measured automatically using VCU-UT program SPI-Team Meeting, Paris, 7.-9.10.98