Gamma-ray Large Area Space Telescope GLAST Large Area Telescope: Balloon Flight Results WBS 4.1.E Tune Kamae Stanford Linear Accelerator Center Stanford University LAT Instrument Technical Manager kamae@slac.stanford.edu On behalf of LAT Balloon Flight Team GSFC, SU-SLAC, SU-HEPL, Hiroshima, NRL, UCSC, Pisa led by D. Thompson, G. Godfrey, S. Williams Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 1
Balloon Flight Results Outline Rationale and Goals Preparation Balloon Flight and Operations Instrument Performance Results vs. Simulation Conclusions Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 2
Rationale: Why a Balloon Flight? NASA Announcement of Opportunity: "The LAT proposer must also demonstrate by a balloon flight of a representative model of the flight instrument or by some other effective means the ability of the proposed instrument to reject adequately the harsh background of a realistic space environment. A software simulation is not deemed adequate for this purpose. Planning the balloon flight: Identify specific goals that were practical to achieve with limited resources (time, money, and people), using the previously-tested Beam Test Engineering Model (BTEM) as a starting point. Fig.1: Beam Test Engineering Model ( 99) (BTEM), a prototype GLAST/LAT tower. The black box to the right is the anticoincidence detector (ACD), which surrounds the tracker (TKR). The aluminum-covered block in the middle is the calorimeter (CAL). Readout electronics were housed in the crates to the left. Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 3
Goals of the Balloon Flight Validate the basic LAT design at the single tower level. Show the ability to take data in the high isotropic background flux of energetic particles in the balloon environment. Record all or partial particle incidences in an unbiased way that can be used as a background event data base. Find an efficient data analysis chain that meets the requirement for the future LAT Instrument Operations Center. Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 4
Preparation:What Was Needed for this Balloon Flight? A detector similar and functionally equivalent to one LAT tower. BTEM Rework on Tower Electronics Module. Stanford U Rework on Tracker. UCSC Rework on Calorimeter. NRL Rework on ACD. GSFC External Gamma Target (XGT). Hiroshima, SLAC On-board software. SLAC, SU, NRL Pressure vessel to keep ~1 atm air for cooling, high voltage, and hard drives. SLAC, GSFC Mechanical structure to support the instrument through launch, flight, and recovery. GSFC, SLAC Power, commanding, and telemetry. NSBF, SU, SLAC, NRL Real-time commanding and data displays. SU, SLAC, NRL Data analysis tools. SLAC, GSFC, UW, Pisa Modeling of the instrument response. Hiroshima, SLAC, KTH Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 5
Preparation: BFEM Integration New Cooler View of XGT Installing the BFEM in Pressure Vessel Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 6
Preparation: Pre-Launch Review X side: Y coordinate 240 160 80 0 80 160 240 Run nsbf 53.27355, xgtcosmic cut, L1t=11410 X Side: Tem/Biu 2010.c4p3.22 190 0 2000.c4p2.16 183 0 +Y 1000.c0p2.12 592 396 Y 2011.c4p0.4 194 1 2001.c4p1.10 450 250 +X Side: Acd/Disks Xgt hit 240 160 80 0 80 160 240 Y side: X coordinate 240 160 Y side: X coordinate 80 0 80 160 240 Run nsbf 53.27355, xgtcosmic cut, L1t=11410 Y X Side: Tem/Biu 000.c2p2.14010.c2p3.20 205 2 179 1 001.c1p3.19011.c1p2.13 521 324 206 1 +X Side: Acd/Disks +Y 240 160 80 0 80 160 240 +X Side: Y coordinate 1200 1000 800 600 400 200 0 Z coordinate 422 390 358 326 294 262 230 198 167 134 102 70 38 0 51 77 104 130 157 183 210 236 263 Run nsbf 53.27355, xgtcosmic cut, L1t=11410 110.c2p0.2 197 2 100.c2p1.8 193 1 TF: xangle=8.41, xerr=0.59 xgtplane x=132.2 xgtsum: 1017 >= 800 2000.c4p2.16 183 0 2001.c4p1.10 450 250 acdsum: 0 <= 3307 <= Inf 1000.c0p2.12 592 396 000.c2p2.14 001.c1p3.19 205 2 521 324 hits: 16<=12x+16y=28<=Inf topz lyr: 0 <= 9 <= Inf botz lyr: 0 <= 1 <= Inf vopenx: 0 <= 0 <= Inf wall margin: 0 <= 0 <= Inf calsum: 33000 <= 34336 <= Inf calhits>ped+20: 0 <= 19 <= Inf max tot: 130 cable=5 cntlr=1 Xgt hit 310.c3p3.21 202 3 300.c1p1.7 207 1 240 160 80 0 80 160 240 Y Side: X coordinate 419 387 355 323 291 259 227 195 163 131 99 67 35 0 51 77 104 130 157 183 210 236 263 Run nsbf 53.27355, xgtcosmic cut, L1t=11410 xgtsum: 1017 >= 800 2001.c4p1.10 2011.c4p0.4 Xgt 450 250 194 1 hit 210.c3p0.3 208 0 200.c3p1.9 203 2 TF: yangle= 6.04, yerr=0.34 xgtplane y= 119.0 acdsum: 0 <= 3307 <= Inf 1000.c0p2.12 592 396 001.c1p3.19 011.c1p2.13 521 324 206 1 hits: 16<=12x+16y=28<=Inf topz lyr: 0 <= 9 <= Inf botz lyr: 0 <= 1 <= Inf vopeny: 0 <= 0 <= Inf wall margin: 0 <= 0 <= Inf calsum: 33000 <= 34336 <= Inf calhits>ped+20: 0 <= 19 <= Inf max tot: 130 cable=5 cntlr=1 410.c0p3.18 209 2 400.c0p1.6 185 3 240 160 80 0 80 160 240 +X Side: Y coordinate Real-time event display. A penetrating cosmic ray is seen in all the detectors. 1200 1000 800 600 400 200 0 Pre-launch testing at National Scientific Balloon Facility, Palestine, Texas. August, 2001. Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 7
Balloon Flight Operations Team at Palestine, Texas Balloon Team at Palestine Texas Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 8
Flight and Operation: Launch on August 4, 2001 The balloon reached an altitude of 38 km and gave a float time of 3 hours. First results (real-time data): trigger rate as a function of atmospheric depth. The trigger rate never exceeded 1.5 KHz, well below the BFEM capability of 6 KHz. Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 9
Flight and Operation: Onboard DAQ and Ground Electronics Worked Realtime event display Document: LAT-PR-00524-02 LAT-PR-00403 Section 4.0 Balloon Flight Results 10 10
Instrument Performance: All Subsystems Performed Properly External Targets (4 plastic scint) to test direction determination and measure interaction rate. 4.5 million L1T recorded on-board and 345k events down linked. ACD (13 scint. tiles) to detect charged particles and heavy ions (Z>=2). CAL (CsI logs) To image EM energy deposition. Tracker (26 layers of SSD) to measure charged tracks 200um and reconstruct gamma ray direction. Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 11
Instrument Performance: All Subsystems Performed Properly Level-1 Trigger Rate (L1T) Level Flight Data Simulation (Geant4) (Cosmic-Ray Fluxes Model) All 500/sec 504/sec Charged 444/sec 447/sec Neutral 56/sec 57/sec Number of Events Recorded Events through Downlink Before Launch 30.5k - Ascending 109k 1.4M Level Flight 105k - Events in Hard Disk Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 12
Instrument Performance: ACD Threshold and Efficiency Nevents 180 160 Tile 310 140 120 100 80 60 0.3 MIP 40 20 0 100 200 300 400 500 600 700 800 900 1000 PHA Anti-Coincidence Detector Pulse height distr. for stiff charged particles shows clean separation of the peak from noise. Scinti. Eff. ~ 99.95% or better* (* One track passed thru the bent part of a tile.) Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 13
Instrument Performance: CAL s Energy Measurement & Imaging Interaction in XGT alpha proton Calorimeter Pulse height distr. for stiff charged particles shows a single-charge peak and a peak due to alpha particles. Alpha particles are seen. Z-X Plane Z-Y Plane Imaging capability demonstrated Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 14
Instrument Performance: Tracker & XGT Association Cosmic ray interaction in 4 External Targets (plastic scintilators) Gamma ray produced in XGT (20 identified) Hadrons produced in XGT (416 recorded) Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 15
Instrument Performance: Mechanical Stability Demonstrated Launch 40 35 3) Landing 60 50 Recovery 30 25 40 20 15 1) 2) 4) 5) 30 20 10 5 10 0 0 500 1000 1500 2000 2500 3000 Time [min] Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 16
Results: Reconstruction of Events Charged particle event: The track passes through the ACD (top), the tracker, and the calorimeter. Note: Tracker has no Si strips in the upper right corner Gamma-ray event: Two tracks are seen in the tracker and calorimeter. Pattern recognition of an inverted V will allow us to selected gamma-rays from cosmic-ray background. Interaction event: Particle and gamma ray splashes deposit energy in ACD, Tracker, and Calorimeter. Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 17
Simulation: Background and Instrument Model Proton spectrum e-/e+ spectra atmospheric gamma spectrum Primary and secondary e-/e+ Primary protons passing into the Earth s magnetic field and secondary protons produced by hadronic int. in the atmosphere Gammas prod. by cosmic-rays interacting in the atmosphere Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 18
Results vs Simulation: Charged Particles Flux & Angular Distribution Model fluxes and angular distributions: protons, muons, and electrons Data γ e-/e+ muons Simulation prediction protons 90 deg. Cosine of cosmic-ray direction Downward Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 19
Results vs Simulation: Charged Particle Distribution Charged particle hit distribution: model fluxes and angular distributions Data Simulation prediction Calorimeter side Tracker layer number Top of Tracker Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 20
Results vs Simulation: Neutral Particle Distribution Neutral particle hit distribution: gammas and under-the-acd electrons Simulation prediction Data Calorimeter side Tracker layer number Top of Tracker Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 21
Conclusions Goals of the balloon flight were achieved. BFEM successfully collected data using a simple three-in-a-row trigger at a rate that causes little concern when extrapolated to the full flight unit LAT. Mechanical robustness of the Tracker design around Silicon Strip Detectors has been verified. Power of segmented Calorimeter design has been demonstrated in identifying gamma rays in charged cosmic ray background. Efficiency of ~99.97% for ACD is shown to be achievable. Through the data analysis, we gained confidence in our ability to simulate the instrument and the cosmic ray background. Balloon flight offered a first opportunity for the LAT team to go through procedures and to face issues typical to a flight program. Lessons learned drawn from BFEM experiences will be fed back to the LAT team. The data are being used to try out the background filter algorithms and reconstruction programs Balloon Experiment has served many purposes and was a success. Document: LAT-PR-00403 Section 4.0 Balloon Flight Results 22