glast lat project calibration & analysis meeting - august 29, 2005 benoît lott gamma-ray large...
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GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope
Response of the GLAST LAT Calorimeter to Relativistic Heavy Ions
http://www.cenbg.in2p3.fr/ftp/astropart/glast/NIM_quenching.pdf
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 <Emax> =25 GeV for a 300 GeV ray
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
Motivation: “quenching”
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
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
Quenching factor: definition
Quenching Factor= Emeas/Edep (normalized to 1 for MIPs)
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
EM ASIC includes preamp, shaping amplifier (3.5 s) , 12-bit ADCAmplitude 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 ionsDetection system includes MWPCs for positionMUSIC (ionisation chamber, Z measurement), plastic scintillation detectors ( A measurement via TOF, trigger)
Three data acquisition systems, with a common trigger signal.
Detector characteristics
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
MUSIC calibration
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
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
E (MeV)
Counts Independent calibration performed by Frederic Pironusing Gaussian+Landaufits
Perfect consistency
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
minical calibration
Same as for EM.
Proton calibration checked against that obtained with:- 22Na g-rays- 20 GeV muons at CERN
In both cases, excellent consistency was found.
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
blue: data red: Geant4
deposited energy (MeV)deposited energy (MeV)
50 GeV e+ 1.5 X080 GeV e+ 1.5 X0
CERN data: deposited energy distributions
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
<Emeas>= (<E+>+ <E->)/2
Quenching factor = <Emeas>/<EGEANT>
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
Longitudinal dispersion by the spectrometer
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
Calculated deposited energy
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
Quenching factor for C: 1.23 “antiquenching”
Quenching factors
Sasha found a similar valuein an independent analysis
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
Quenching factors
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
-particle measurement
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
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
Compilation of quenching factors
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.
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
Scintillation components
measured with a standard phototube
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
Hamamatsu S3590
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
Scintillation components
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
Ion selection with MUSIC(ionization chamber)
The ionization peaks correspondto non-interacting ions.
Loss to reactions
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
Loss to reactions
GLAST LAT Project Calibration & Analysis Meeting - August 29, 2005
Benoît Lott
Charge-changing cross sections
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/nucleonis 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).