Operation of Ideal Gains - Calorimeter

Note: 'official' status and values can always be found here http://www-glast.stanford.edu/cgi-bin/viewcvs/CalXtalResponse/xml/

CURRENT VALUES - Ideal flight mode

Ideal mode calibrations are based on measured means of cal Flight Models.

They are not well suited to real data as they treat all crystals as equal, while the varying pedestals in real
data could cause some ideal calibrations to be out of range.

'flight' mode calibrations are intended for simulating flight energy levels.

The effective reponse of the current configuration is as follows

NEWIDEAL_FLIGHT3 (CalXtalResponse v0r6p6, 7/21/05 expected GlastRelease > v6r9)
- NOTE: all ADC units are pedestal subtracted
RANGE MeV/ADC MAX_ADC SATURATION(MEV)  PED(ADC) NOISE(ADC,MeV) LAC(ADC,MeV)  FLE(ADC,MeV) FHE(ADC,MeV)
LEX8  0.03    3550    109              510      13.3, 0.4      66.6, 2.0     3333,100
LEX1  0.27    3850    941              210      1.48, 0.4                 
HEX8  2.16    3550    7676             510      6.0,  12.96                               463,1000
HEX1  19.23   3850    74,016           210      0.6,  11.5

it incoperates the following improvements over the prievous version.

increase of noise & LAC thresholds to better approximate real flight expectations
enabling of FLE & FHE trigger simulation

CURRENT VALUES - Ideal muon mode

ideal mode calibrations are based on measured means calibrations of real Cal flight models.

They are not well suited to real data as they treat all crystals as equal, using them w/ the varying pedestals in real
data could cause some calculations to go out of range.

'muon' mode calibrations are simply average values from ground muon collections.

The effective reponse of the current configuration is as follows

NEWIDEAL_MUON2 ( CalXtalReponse v0r2p6, GlastRelease v6r4 -> v6r9 ....current)
- NOTE: all ADC units are pedestal subtracted
- NOTE: FLE & FHE values added in CalXtalResponse v0r6p6
RANGE MeV/ADC MAX_ADC SATURATION(MEV)  PED(ADC) NOISE(ADC,MeV) LAC(ADC,MeV) FLE(ADC,MeV)  FHE(ADC,MeV)
LEX8  0.03    3550    106.5            510      6.0, 0.18      43, 1.29     333,10
LEX1  0.27    3850    958.5            210      0.6, 0.162                 
HEX8  0.17    3550    569.5            510      6.0, 1.02                                  176,30
HEX1  1.53    3850    5890             210      0.6, 0.92

it incoperates the following improvements over the prievous version.

ULD values for all ranges and HEX1 saturation level are set to very close to 4095. The previous values were lower in an effort to avoid problems caused by channels w/ higher pedestals which is not an issue in ideal mode
LAC threshold was raised to 1.3 MeV which is closer to the mean LAC threshold used for flight crystals
pedestal noise levels are lower to better reflect the true behavior of the flight front-ends
some values were rounded a bit just to make things simpler.

HISTORY OF VALUES

This documents the history of CalXtalReponse ideal calibrations.

NEWIDEAL_FLIGHT2 (CalXtalResponse v0r3p1 -> v0r6p5, GlastRelease v6r6p0416 -> v6p9)
- NOTE: all ADC units are pedestal subtracted
RANGE MeV/ADC MAX_ADC SATURATION(MEV)  PED(ADC) NOISE(ADC,MeV) LAC(ADC,MeV)
LEX8  0.03    3550    109              510      6.0, 0.18      43, 1.29     
LEX1  0.27    3850    941              210      0.6, 0.162                 
HEX8  2.16    3550    7676             510      6.0, 12.96                 
HEX1  19.23   3850    74,016           210      0.6, 11.52  

it incoperates the following improvements over the prievous version.

- HE gain setting is set to maximum energy range, raising single xtal saturation level.
- ULD values for all ranges and HEX1 saturation level are set to very close to 4095.  The previous values were lower in an effort to avoid problems caused by channels w/ higher pedestals which is not an issue in ideal mode
- LAC threshold was raised to 1.3 MeV which is closer to the mean LAC threshold used for flight crystals
- pedestal noise levels are lower to better reflect the true behavior of the flight front-ends
- some values were rounded a bit just to make things simpler.

Note: CalXtalResponse v0r3 was incorrect

NEWIDEAL_FLIGHT (CalXtalReponse v0r2p8 -> v0r2p7, GlastRelease v6r6 -> v6r6p1)
- NOTE: all ADC units are pedestal subtracted
RANGE MeV/ADC MAX_ADC SATURATION(MEV)  PED(ADC) NOISE(ADC,MeV) LAC(ADC,MeV)
LEX8  0.03    3400    109              510      5.1, 0.153     30, 0.9     
LEX1  0.27    3400    941              210      2.1, 0.567                 
HEX8  1.73    3400    5913             510      5.1, 8.823                 
HEX1  15.38   3400    52,000           210      2.1, 32.30                 

NEWIDEAL_MUON2 ( CalXtalReponse v0r2p6, GlastRelease v6r4 -> v6r5)
- NOTE: all ADC units are pedestal subtracted
RANGE MeV/ADC MAX_ADC SATURATION(MEV)  PED(ADC) NOISE(ADC,MeV) LAC(ADC,MeV) 
LEX8  0.03    3400    109              510      5.1, 0.153     30, 0.9     
LEX1  0.27    3400    941              210      2.1, 0.567                 
HEX8  0.17    3400    591              510      5.1, 0.867                 
HEX1  1.53    3400    5,200            210      2.1, 3.213                 

NEWIDEAL_MUON1 ( CalXtalReponse v0r2 -> v0r2p5, GlastRelease <= v6r3p2 )
- NOTE: all ADC units are pedestal subtracted
RANGE MeV/ADC MAX_ADC SATURATION(MEV) PED(ADC)  NOISE(ADC,MeV) LAC(ADC,MeV)
LEX8  0.03    3500    112             510       5.1, 0.153     30, 0.9     
LEX1  0.27    3500    968             210       2.1, 0.567                 
HEX8  0.17    3500    608             510       5.1, 0.867                 
HEX1  1.53    3500    5,352           210       2.1, 3.213

HOW IT WORKS

basically, there are two stages.

Recon
1) ADC->DAC
2) DAC->MEV

digi is the opposite of course, but it is done in pieces. first the dac 'scale' values for the individual McIntegratingHit energies are summed together, once they're all summed, then we convert dac->adc.

here are the constants from CalXtalResponse/xml/idealCalib.xml file.

<item name  = "LARGE"      value = "0.36"> Large diode MevPerDac </item>
<item name  = "SMALL"      value = "2.0">  Small diode MevPerDac </item>


 <item name = "ADC_PER_DAC" value = "11.2, 1.3, 11.5, 1.3"> ADC/DAC

for each ADC range </item>

so for LEX8 recon would go something like this:

dac = adc/11.2  // 11.2 is the LEX8 val for adc_per_dac mev = dac*0.36  // using large diode MevPerDac.

so final ratios are:

LEX8 ADC/Mev = 0.0321
LEX1         = 0.27
HEX8         = 0.17
HEX1         = 1.5

all ranges are currently maxing out at 3500 ADC (including pedestals) pedestals are about 500 in X8 and 200 in X1 this makes the max measurable energy in HEX1 (3500-200)/1.5=2.2gev per xtal. i don't know if that's a problem or not, like i said before these numbers are averages from muonCalib which uses different gain settings from flight.

incidentally, all these values can be changed instantly by editing the idealCalib.xml file (so you can see the effect of changing gains, peds, etc...).