1. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Gamma-ray Large Area Space Telescope Response of the GLAST LAT Calorimeter to Relativistic Heavy Ions http://www.cenbg.in2p3.fr/ftp/astropart/glast/NIM_quenching.pdf

2. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Energy calibration and response monitoring of the calorimeter: energy deposits of cosmic-ray heavy ions (C,N,O,Si,Fe) Introduction magnetic cutoff + “logarithmic-rise” domain: well-defined peaks in deposited energy per log Fe: peak at 7.7 GeV =25 GeV for a 300 GeV  ray

3. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Motivation: “quenching”

4. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Temporal dependence of light ouput p: fast+slow comp. ions: fast comp. only low energy

5. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Quenching factor: definition Quenching Factor= E meas /E dep (normalized to 1 for MIPs)

6. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott EM ASIC includes preamp, shaping amplifier (3.5  s), 12-bit ADC Amplitude sampled through a Track&Hold stage at fixed delay time after the trigger signal minical: 8 layers of 3 log each, with discrete electronics similar as EM, but with a 12-bit peak-sensing ADC Fragment Separator (FRS) 1.7 GeV/nucleon Ni on Be target: 4 dipole magnets: selection of particles according to magnetic rigidity (p/Q) “Cocktail” beam of A/Z=2 ions Detection system includes MWPCs for position MUSIC (ionisation chamber, Z measurement), plastic scintillation detectors ( A measurement via TOF, trigger) Three data acquisition systems, with a common trigger signal. Detector characteristics

7. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott MUSIC calibration

8. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott EM calibration - non-linearity correction - pedestal subtraction - LEX8 absolute calibration - LEX1, HEX8, HEX1: cross calibration of adjacent ranges

9. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott E (MeV) Counts Independent calibration performed by Frederic Piron using Gaussian+Landau fits Perfect consistency

10. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott minical calibration Same as for EM. Proton calibration checked against that obtained with: - 22 Na g-rays - 20 GeV muons at CERN In both cases, excellent consistency was found.

11. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott blue: data red: Geant4 deposited energy (MeV) 50 GeV e + 1.5 X 0 80 GeV e + 1.5 X 0 CERN data: deposited energy distributions

12. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Quenching determination Ion selection with MUSIC (ionization chamber) Gaussian fits of ionization peaks independently for two log ends = ( + )/2 Quenching factor = /

13. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Longitudinal dispersion by the spectrometer

14. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Calculated deposited energy

15. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Quenching factor for C: 1.23 “antiquenching” Quenching factors Sasha found a similar value in an independent analysis

16. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Quenching factors

17. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott  - particle measurement

18. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Energy resolution Another difference between MIPs and heavy ions 0.6 MeV/12 MeV = 5% extra width for MIPs much less (< 1%) for heavy ions

19. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Compilation of quenching factors

20. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Possible interpretation of the antiquenching effect, based on an extrapolation on what is known at low-energy For MIPs, part of the energy goes into a slow scintillation component, that could be absent for heavy ions. This slow component is essentially filtered out by our electronics, resulting in the measured energy being lower for MIPs than for heavy ions.

21. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Scintillation components measured with a standard phototube

22. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Hamamatsu S3590

23. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Scintillation components

24. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Ion selection with MUSIC (ionization chamber) The ionization peaks correspond to non-interacting ions. Loss to reactions

25. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Loss to reactions

26. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Charge-changing cross sections

27. GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005 Benoît Lott Conclusion The CsI response to relativistic ions has been measured. The “antiquenching” effect was unexpected, but is compatible with the trend observed at lower energy. Data measured up to 1.7 GeV/nucleon: 90% of CR ions will have E<10 GeV/nucleon. Negligible change of quenching factors between 1 GeV and 1.7 GeV/nucleon (dE/dx changes by 7%). The assumption that they remain constant up to 10 GeV/nucleon is reasonable. Overall uncertainty ~ 3%. The scintillation components observed with a standard phototube are similar for MIPs and Carbon ions (worth repeating with a red-sensitive phototube).