GLAST LAT Project I&T Meeting – Jan 20,2004

E. do Couto e Silva 1

GLAST Large Area Telescope: GLAST Large Area Telescope: EM1 Data Analysis and Calibration

Summary Report

Eduardo do Couto e SilvaSU-SLAC

SVAC I&T Manager

eduardo@slac.stanford.edu650-926-2698

Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope

GLAST LAT Project I&T Meeting – Jan 20,2004

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SVAC EM RequirementsSVAC EM Requirements

The Engineering Model (EM1) was used to develop the necessary infrastructure for future hardware tests. Requirements and goals

were described in the (“SVAC EM Plan” LAT-TD-00573)

– SVAC EM requirements

Develop infrastructure for TKR and CAL calibrations Measure the energy spectrum of van de Graaff photons

– SVAC EM goals

Exercise flexibility of geometry input for the Monte Carlo simulations.

Validate a preliminary set of Monte Carlo distributionsPrototype energy resolution algorithm Prototype alignment algorithm

GLAST LAT Project I&T Meeting – Jan 20,2004

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Data Analysis ChainData Analysis Chain

ROOT tree Files(digi)

SAS/ONLINE

Converter

ROOT tree Files

(recon)

SASRecon

“GENERAL”USER

OnlineAnalysis tools

onlinescripts

Calibration Constants

Calibrationscripts

ROOT ntuplefiles

IDL Structures

SASConverter

SASUser Interface

EBFEM

In the future the FSW Filter will go in here

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EM CalibrationsEM Calibrations

• TKR Determine Operational Thresholds Measure Electronic Gain Identify noisy and dead strips Characterize TOT

– Slope and intercept with charge injection – Mean and width of distributions

• CAL Determine Operational Thresholds (HI, LO and zero

suppression) Measure pedestal and gains

– Identify noisy and dead logs Determine muon peak position and width Measure light Asymmetry, Attenuation, Yield

Measure position resolution without TKR tracks Measure position resolution with TKR tracks

Present status: 3 months after the end of the data taking period

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Calibrations – To do ListCalibrations – To do List

SVAC ID Description Comments

  C10 TKR Noisy Channels EGSE   SAS recon Need to define noise level

  C11 TKR Dead Channels EGSE   SAS recon  

  C12 TKR ToT Signal EGSE CI   PID? Seen variations on channel by channel. Maybe used for particle ID

  C13 TKR ToT Distribution     SAS PID? Maybe used as a cross check of C12

  C14 CAL Light Asymmetry     SAS recon Would like to change this to Energy Scale (MeV/ADC count)

  C15 CAL Light Attenuation     SAS recon Measure muon peaks (includes effects from optical and electronic gains). Function of position in a log. Investigating light taper model

  C16 CAL Light Yield EGSE CI I&T has no experience, done by CAL only. Need to capture information for offline

  C18 CAL Pedestals EGSE CI SAS recon Need to define width characterization (rms vs sigma)

  C19 CAL Electronic Gain EGSE CI     Need to get information from online

  C20 CAL Integral non-linearity EGSE CI     Need to get information from online

  C22 CAL Noisy Channels EGSE   SAS   From pedestal widths. None observed in EM. Need to develop infrastructure

  C23 CAL Dead Channels EGSE CI SAS   From pedestal widths. None observed in EM. Need to develop infrastructure

  C24 CAL LO Discriminator EGSE CI     I&T has no experience, done by CAL only. Need to capture information for offline

  C25 CAL HI Discriminator EGSE CI     I&T has no experience, done by CAL only. Need to capture information for offline

  C26 CAL Zero-Suppress Threshold

EGSE CI     I&T has no experience, done by CAL only. Need to capture information for offline

  C27 Deadtime EGSE       Measure overall deadtime as part of the functional test plan

  C29 TKR GTFE Threshold Scan EGSE CI     Need to capture information for offline including GTFE split

Calibration List derived from Level III document – SVAC EM Plan – LAT-MD-00446

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Calibration InfrastructureCalibration Infrastructure

TasksLessons learned

Develop code to create constants from the digi files•Redefined output format as we learned more about the instrument

Develop code to read constants into recon•Modified reconstruction to allow calibrations without zero suppression in the CAL•Modifying reconstruction to read in ToT constants on channel per channel basis•Developing a scheme to capture the instrument configurations necessary for MC validation and for reference during calibrations

Configuration control•Created cvs repository to keep the calibration code •Developing process to version control creation of constants and to transfer information from online whenever needed

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Energy MeasurementEnergy Measurement

ROOT tree Files(digi)

Raw spectrum of individual crystals

Calibration Constants

Perform Calibrations C14,C15,C16,C18 on each crystal

Operational Settings Perform C18,C19,C20,C22,C23,C24 to establish baseline for data taking

ROOT tree Files

(recon)

Produce Energy Calibrated Spectrum using all crystals

ROOT ntuplefiles

IDL Structures

Use Data Analysis Cuts and VDG Flux Calibration to obtain final

spectrum

Data Analysis

Calibrations

GLAST LAT Project I&T Meeting – Jan 20,2004

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CAL Energy SpectrumCAL Energy Spectrum

1 10 100 1000

400

300

200

100

0

1 10 100 1000

2500

2000

1500

1000

500

0

Photon Source OFF

Photon Source ON

Energy (MeV)

Mostly photons

From Gary Godfrey

GLAST LAT Project I&T Meeting – Jan 20,2004

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Source CalibrationSource Calibration

From Gary Godfrey

Expect two energy lines

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Flux MeasurementFlux Measurement

01.0093.0

)15.0(35.131152)202.0(

1200

srHzssr

N

N

BGO

BGO

EM

EM

Top TKR face Extrapolation to Photon Source

 

EM Rec Direction cosineIn 0.02 bins

15.0)84.21(4

4)6(2

180

45cos

9

7

2

cm

ecm

pipet

BGO

10% error is dominated by the knowledge on the

BGO position

9% of the of photons produced by the source are measured by the EM

From Gary Godfrey

GLAST LAT Project I&T Meeting – Jan 20,2004

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Experimental setupExperimental setup

CAL TKR

Gammas:66% 17.6 MeV 34% 14.6 MeV, FWHM = 1.5 MeV

+ lots of electrons

Cosmic Background

Electrons are produced by gamma conversions in the iron shield in front of the accelerator

Beam pipe

Not a monochromatic beam!

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EM Energy Spectrum (VDG DATA)

Event selection: nTkrTracks>=1 && zDir < -0.9 (25 deg from vertical) && maxCal>4MeV

Expected SpectrumDelta function (17.6 MeV)Breit-Wigner (mean 14.5,

width=1.5MeV)

Energy (MeV)

From Xin Chen

GLAST LAT Project I&T Meeting – Jan 20,2004

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Energy Spectrum (VDG MC)Energy Spectrum (VDG MC)

Events converted in top layer ofTracker only

From Xin Chen

Event selection: nTkrTracks>=1 && zDir < -0.9 (25 deg from vertical) && maxCal>4MeV

Expected SpectrumDelta function (17.6 MeV)Breit-Wigner (mean 14.5,

width=1.5MeV)

Energy (MeV)

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Documentation for EM2Documentation for EM2

We are now updating the following documents SVAC EM Plan – LAT-MD-00573

•Defines the SVAC requirements

Calibration algorithms for the EM – LAT-TD-01588•Describes Algorithms•Describes Output Formats for the calibration data

LAT SAS EM Calibration Infrastructure – LAT-TD-01340•Describes the SAS database and how calibrations are used by the offline code

SVAC Database for the EM – LAT-TD-00578•Describes how calibration data is stored in ORACLE for trending

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SummarySummary

Current status 3 months after the end of the data taking period

• Calibrations– We have met all calibration requirements – Lessons learned on the infrastructure are now being implemented

for EM2

• Data Analysis– We have met the requirements for the measurement of the energy

spectrum– In addition we met most of the goals for the EM1 including the

development of an algorithm for energy resolution, which is now being documented and will be presented in detail in the near future by Xin Chen for a group review

• Documentation– We have started updating all documentation relevant to EM2