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

SPI-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, 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 (Plan) SPI-MPE-RP (Report, in preparation)

SPI-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, ACS EM

SPI-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, 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 cm 3 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 UU Q R C

SPI-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, LED-Dummy

SPI-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, BGO Crystal Detector Module

SPI-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, 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-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, FEE-Unit Tester with FEE and LED-Dummy

SPI-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, VCU - Unit Tester

SPI-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, Linearity of Event-Trigger Thresholds

SPI-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, Linearity of Energy Thresholds

SPI-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, 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-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, Single Photoelectron (SPE) Spectrum using LED Dummy PMT : HV nominal (1129 V) HV low (1088 V) HV high (1170 V)

SPI-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, 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 (  0.3 x ) Cb generated at photocathode SPE spectrum from LED with a different FEE corresponds to 2.0x (  0.3 x ) Cb Yresults consistent with expected values (single photoelectrons!) !! So far SPEs measured only using LED Dummy !!

SPI-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, Ab hier „Reservefolien“

SPI-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, Detail ACS EM LED-Dummy and „Crystal Dummy“

SPI-ACS EM MeasurementsCornelia Wunderer, MPESPI-Team Meeting, Paris, LED - SPE Spectrum measured automatically using VCU-UT program