AMS-02 Anticounter. Philip von Doetinchem I. Physics Institute B, RWTH Aachen Bad Honnef, August 2007

Transcription

1 AMS-02 Anticounter Philip von Doetinchem I. Physics Institute B, RWTH Aachen Bad Honnef, August 2007

2 Michael Griffin, NASA Head AMS does not have a shuttle flight! Philip von Doetinchem AMS-02 Anticounter Aug p. 2

3 Library of Congress, July 2007 The Alpha Magnetic Spectrometer (AMS) will enable an ambitious, scientifically compelling experiment to investigate antimatter. Despite NASA's long-standing commitment to this unique experiment, the NASA Administrator last year stated that NASA would no longer commit to flying AMS to the International Space Station (SS) on the space shuttle. The Committee is disappointed that NASA has chosen to cancel the flying of this highly rated scientific experiment that would make use of the unique capabilities of the ISS. The Committee directs the Administrator to study the possibility of delivering the AMS to the ISS. This study should include the options considered, an analysis of those options, identify the preferred option including its cost and schedule, and how such an option could be implemented. This study should be submitted to the Committee within nine months of the enactment of this Act. Philip von Doetinchem AMS-02 Anticounter Aug p. 3

4 Cosmic Rays in the GeV Range good agreement of data and propgation models, but some unexplained features in the antiparticle/photon fluxes some theories exist to explain a possible excess, but need validation with cosmic rays and LHC so far no antimatter was found in cosmic rays Philip von Doetinchem AMS-02 Anticounter Aug p. 4

5 AMS02 Overview Goals of AMS02: precise spectroscopy of cosmic rays without interactions with atmosphere on the International Space Station measurement/bounds on antimatter indirect dark matter search Subdetectors: Transition Radiation Detector (TRD) particle identification Time of Flight (ToF) trigger, velocity, charge Tracker track reconstruction, momentum Anti-Coincidence Counter (ACC) particle selection next slide Ring Image Cherenkov Detector (RICH) precise velocity mesaurement Electromagnetic Calorimeter (ECal) particle identification Philip von Doetinchem AMS-02 Anticounter Aug p. 5

6 ACC System avoid wrong charge reconstruction in tracker small ACC inefficiency needed (< -4 ) for measurement of antimatter with very clean single tracks Philip von Doetinchem AMS-02 Anticounter Aug p. 6

7 ACC parts 16 Saint Gobain Scintillator Panels with inlaying Bicron wave length shifting fibers 16 Y-shaped Toray clear fiber cables PMT side 16 Hammamatsu fine mesh PMTs panel side Philip von Doetinchem AMS-02 Anticounter Aug p. 7

8 Cosmic Test in the Lab ACC panel trigger on central region 0 missed out of triggers Extrapolation gives inefficiency of: upper limit (1σ) ineffciency = T1 ACC T2 granite table T3 Philip von Doetinchem AMS-02 Anticounter Aug p. 8

9 ACC Testbeam: T9 East Area, p + GeV Philip von Doetinchem AMS-02 Anticounter Aug p. 9

10 Systematic views on the setup y central region slot region Test in two configurations: overlap region of panels central region Philip von Doetinchem AMS-02 Anticounter Aug p.

11 Testbeam results Ch 26 Ch 26 entries [#] 4 pedestal central Ch 28 entries [#] 3 raw signal central Ch ADC counts [#] ADC counts [#] Cut for efficiency calculation: 3 times pedestal width = 6 adc channels Philip von Doetinchem AMS-02 Anticounter Aug p. 11

12 Testbeam results ADC counts [#] black histogram: all 4 PMTs over certain threshold Y Position [mm] PMT on lower panel has only pedestals starting from slot to upper panel Philip von Doetinchem AMS-02 Anticounter Aug p. 12 1

13 Signals in different regions Sum of ADC counts from both PMTs on one panel entries: entries: entries: entries [#] 3 mean: 1.3 rms: 39.3 entries [#] 2 mean: 92.1 rms: 47.9 entries [#] mean: rms: 22.9 entries [#] total ADC counts [#] total ADC counts [#] total ADC counts [#] total ADC counts [#] slot 2.6 mm from slot 6.6 mm from slot central Philip von Doetinchem AMS-02 Anticounter Aug p. 13

14 Panel Status panels waiting for test test with atmospheric muons AMS02 ACC AMS01 ACC trigger all panels are readily produced and tested with reference PMTs Philip von Doetinchem AMS-02 Anticounter Aug p. 14

15 Testing Procdure entries [#] 8 panel distribution Entries 20 Mean RMS entries [#] channel 0 channel 1 entries [#] cosmics 1 LED number of photo electrons[#] adc measurement of MOP with cosmics calibration with LEDs implemented in panels adc 1 st ACC: new panels are 45% better due to better glueing calculation of photo electron number N pe = Q Q σ C LED 2 LED Philip von Doetinchem AMS-02 Anticounter Aug p. 15

16 Thermo Vacuum Test TVT tank temperature [deg C] Temperature on voltage divider -20 PMTs pressure [mbar] time [h] pressure during test time [h] Temperature requirements: operative: C non-operative: C All PMTs are tested! Philip von Doetinchem AMS-02 Anticounter Aug p. 16

17 Vibration Test PMTs famous old Professor Vibration table 5 PMTs sucessfully tested, rest to come... Philip von Doetinchem AMS-02 Anticounter Aug p. 17

18 PMT results mop Classification of PMTs with: number of photo electrons MOP value for cosmics (1900V) pe before all tests, temp/final voltage divider (mv/adc) after tvt batch 3, final voltage divider after tvt batch 2, final voltage divider after vibration batch 1, final voltage divider PMT 18 before tests, ftemp/final voltage divider (mv/adc) PMT 18 before tests, temp/final voltage divider (mv/adc) PMT 18 after vibration & TVT, temp/final voltage divider (mv/adc) fine mesh PMTs don t show a clear correlation between photo electron number and signal height calibration with gain curves so far: enough good PMTs flight PMTs have 25% more photo electrons Philip von Doetinchem AMS-02 Anticounter Aug p. 18

19 Fiber Physics Optimization of fiber coupling: wave length shifting fiber (WLS) to clear fiber large angular acceptance and small attenuation needed acceptance of fiber is described by numerical aperture (NA): sinθ max number of modes in plastic optical fibers (POF): damping is mode dependent 2 2 ncore ncladding = large attenuations in higher modes (longer way in cladding, more reflections)! local NA not very useful! Philip von Doetinchem AMS-02 Anticounter Aug p. 19 N = 1 2 a 2π NA λ 6 NA

20 Fiber Physics Coupling damping: NA CE = NA log NA WLS clear Photon reabsorption in WLS fibers: broadening of angular farfield distribution larger attenuation Philip von Doetinchem AMS-02 Anticounter Aug p. 20 2

21 Fiber Test Results (POFAC Nürnberg) Output WLS fiber, panel Bicron acceptance: Toray acceptance: damping 3.7dB (40%) damping 1.5dB (70%) entries [#] x Profile y Profile entries [#] x Profile y Profile entries [#] x Profile y Profile angle [deg] angle [deg] angle [deg] Philip von Doetinchem AMS-02 Anticounter Aug p. 21

22 Isotropic Particle Distribution in Panels entries [#] beamtest: straight infall to panel travelled path [cm] space: isotropic particle distribution leads to longer path length in scinitillator random factor on measured charge according to the folding of the isotropic particle distribution and the travelled path length Philip von Doetinchem AMS-02 Anticounter Aug p. 22

23 Efficiency of ACC center region slot region mean inefficiency = 4-6 Estimated mean inefficiency of one complete ACC panel with clear fiber connection, larger signals for new panels & PMTs, isotropic dis., but with testbeam elec.: 4-6 Philip von Doetinchem AMS-02 Anticounter Aug p. 23

24 Upcoming complete sytem test complete system test: 2 flight panels connected to one Y-shaped clear fiber cable running to the finally tested PMTs test and readout of 4 panels in parallel calibration of panels LEDs of each combination with cosmics Philip von Doetinchem AMS-02 Anticounter Aug p. 24

25 Electronics SFEA2 board Pouxe Chip Test with ACC panel & PMTs SFEA2: 1 branch: measurement of charge in ADC after the Pouxe chip 1 branch: comparator with adjustable threshold for trigger and time information in TDC Amplifier before ADC Philip von Doetinchem AMS-02 Anticounter Aug p. 25

26 SFEA2 Tests Calibration of ADC test pulse, Gain 25, 1kΩ signal/noise = (ADC-ped)/σ ped nF 5nF testbeam charge [pc] preamplifier gives good resolution for charge determination better charge resolution than in beamtest for small charges due to the nonlinearity of the Pouxe chip will be useful for the slot region of ACC with small signals Philip von Doetinchem AMS-02 Anticounter Aug p. 26

27 Cosmic Spectra with SFEA2 Cosmic spectrum good charge resolution and small pedestal for constant event rate, but problems with pedestal shifts with event rate (resonsibilty of Bologna group) comparator branch seems to work as expected, but more careful study needed TDC on SFEA2 need more investigation (responsibilty of Bologna group) Philip von Doetinchem AMS-02 Anticounter Aug p. 27

28 Conclusion flight production is nearly finished tests were successful, only few tests missing required inefficiency is achieved to assure a very clean track reconstruction preintegration of ACC CERN this September tests with the final electronics final integration in March 2008 Philip von Doetinchem AMS-02 Anticounter Aug p. 28

29 Failure is not an Option! Philip von Doetinchem AMS-02 Anticounter Aug p. 29