Instrumentation Issues

Transcription

1 Gamma-Ray Large Area Space Telescope GLAST Instrumentation Issues Hartmut F.-W. Sadrozinski SCIPP, Univ. of California Santa Cruz

2 Through most of history, the cosmos has been viewed as eternally tranquil 2

3 ` During the 20 th century the quest to broaden our view of the universe has shown us the vastness of the Universe and revealed violent cosmic phenomena and mysteries 3

4 GLAST GLAST measures the direction, energy & arrival time of celestial gamma rays - LAT measures gamma-rays in the energy range ~20 MeV - >300 GeV - GBM provides correlative observations of transient events in the energy range ~20 kev 20 MeV -Launch vehicle: Delta-2 class - Orbit: 550 km, 28.5o inclination - Lifetime: 5 years (minimum) Hartmut F.-W. Sadrozinski, SCIPP VCI

5 Si Tracker pitch = 228 µm channels 18 planes (16 with converters) GLAST LAT γ ACD segmented scintillator tiles CsI Calorimeter hodoscopic array (8 layers) channels e + e - DAQ, FSW, ELEX Grid mechanical thermal LAT: 4 x 4 modular array 3000 kg, 650 W 20 MeV 300 GeV 5

6 Tracker Production Overview Module Structure Components SLAC: Ti parts, thermal straps, fasteners. Italy (Plyform): Sidewalls SSD Procurement, Testing Japan, Italy (HPK) SSD Ladder Assembly Italy (G&A, Mipot) Tracker Module Assembly and Test Italy (Alenia Spazio) 18 10,368 Tray Assembly and Test Italy (G&A) 2592 Readout Cables UCSC, SLAC (Parlex) Electronics Fabrication, burn-in, & Test UCSC, SLAC (Teledyne) Composite Panel, Converters, and Bias Circuits Italy (Plyform): fabrication SLAC: CC, bias circuits, thick W, Al cores 6

7 Silicon-Strip Detectors SSD 11.5 k SSD from 6 wafers by Hamamatsu 400 µm thick, single sided, p-on-n 8.95 cm 8.95 cm (6 wafers) Strip pitch: 228 µm AC coupled with polysilicon bias (~60MΩ) 800k readout channels > 5M bonds HPK tested: Detector I-V curve Detector C-V curve Integrety of strip Coupling C, Bias R Guaranteed wafer cut to 20um GLAST LAT tested I-V curve and Coupling C after bonding Result from the mechanical alignment Leakage current ~ 100nA/SSD Bad Channel count: Specification: < 0.1% Produced < 0.01% After Bonding < 0.02% 7

8 GLAST Challenge: Interconnects Tray with 1 ladder and MCM Bond Ladder Gluing/Bonding Ladder leakage current at 150V: sum of SSDs (green).,after ladder leakage wire current 150V after encapsulation ladder SSD encaps. na Flex Cable ladder number 8

9 Engineering Model TKR From Balloon Flight Tower - used in beam test and Sub-orbital balloon flight-....to the Engineering Model used in technology validation shake and bake 9

10 Calorimeter Overview Photo-Diodes (HPK) Detector Assembly (NRL/Swales) CsI Crystals (Sweden) C-Composite Structure (France) Electronics & Assembly (NRL) 10

11 GLAST Science Opportunities Active Galactic Nuclei Isotropic Diffuse Background Radiation Endpoints of Stellar Evolution Neutron Stars/Pulsars Black Holes Cosmic Ray Production: Identify sites and mechanisms Unidentified Gamma-ray Sources Gamma-Ray Bursts Dark Matter Solar Physics DISCOVERY! 11

12 Scientific Heritage: CGRO-EGRET EGRET All-Sky Map (E> 100MeV) Cygnus Region 3C279 Vela Geminga Cosmic Ray Interactions With ISM PSR B Crab PKS LMC PKS

13 GLAST Survey: 3 rd EGRET ~10,000 ~300 Catalog sources (2 (2 days) years) GRB, AGN, 3EG + Gal. plane & halo sources 13

14 14

15 Gamma-Ray Bursts LAT FoV GLAST LAT GRB Location Accuracy GBM FoV Norris et al GLAST will probe the time structure of GRB s on the µs time scale Spectral and temporal information might allow observation of quantum gravity effects. Expected Numbers of GRBs and Delayed Emission in GLAST Time between detection of photons 15

16 LAT Science Capabilities - Resolution Unidentified EGRET Sources Greatly improved source localization will aid the search for counterparts and the identification of sources. Source localization (68% radius): γ bursts Unidentified EGRET sources 0.3 to 1 1 to tens of arcmin Cygnus region (15 0 x 15 0 ), Eγ > 1 GeV M31 > 1 GeV Expect 50 x more sensitivity for GLAST than for EGRET 16

17 Gamma-Ray Detection gamma Veto counters: a signal indicates presence of a charge cosmic ray, instead of a photon. Veto counters Converters Gamma Cross-Section is in Pair Production for E γ > few MeV e- Reconstruct Vertex e+ Calorimeter Position-sensitive detectors Tracker/Converter: heavy metal converts the photon to a positron-electron pair. The measured tracks point back to the astronomical source. Calorimeter: measures the photon energy Converter Thickness t Rate: A eff ~ t Pointing Error: Low E: PSF ~ t/e (Multiple Scattering) High E: PSF ~ Detector RMS Many thin Converters ($$) High Precision Detectors ($$) 17

18 Lessons Learned: EGRET - GLAST EGRET GLAST LAT Performance Parameter Instrument Monolithic Modular 4 x 4 Tower Effective Area A eff TKR Monolithic 4 x 4 Tower Trigger, A eff CAL Monolithic Hodoscopic Bkgrd. Reduction, Long. Profile ACD Monolithic Segmented Self-veto, Bkgrd. Reduction Trigger TOF TKR or CAL or ACD Field of View (FoV) TKR Techn. Spark Chamb. Silicon Strip Detector Dead Time, PSF, Trigger, Services, Press. Ves. Life time, 18

19 Instrumentation -> Performance Angular Resolution PSF Spark Chambers vs. SSD Angular Acceptance = FoV TOF Trigger vs. SSD & CsI Self Trigger

20 Instrumentation -> Performance Rate A eff Modular Towers vs. Monolithic Pressure Vessel Monolithic Veto Energy Resolution Monolithic NaI vs. Hodoscopic CsI

21 EGRET WCC / VCI - GLAST AO LAUNCH GLAST CONCEPT R&D C O N S I & T WCC X H I AO LAUNCH DO EGRET CONCEPT R&D CONSTRUC TION I & T W A I T SCIENCE

22 Compton Gamma-Ray Observatory April 5, Launch and Deployment 22

23 Compton Gamma-Ray Observatory June 4, 2000 re-entry burn-up up 23

24 Moore s Law for SSD Silicon Area [m 2 ] GLAST ATLAS NOMAD D0 AMS-02 Agile MEGA LEP AMS-01 CDF BaBar LPS Mark2 CDF Pamela Year CMS Cost /Area [ $/cm 2 ] Cost /Area of Single-sided Silicon Strip Detectors (double-sided factor 2.5 higher) 100 SSD Area increased exponentially SSD Cost decreases exponentially (simpler, robust design simpler specs Q/A) 10 Mark 2 DC coupl. ZEUS DC coupl. Nomad (untested) 4 " Blank Wafer Price 6 " Year GLAST "4" Wafer Size GLAST 6" ATLAS CDF CMS 4" 6"

25 Limited Resource: Power Silicon Area vs. # of Electronics Channels Area [m 2 ] CMS Space GLAST ATLAS AMS-02 NOMAD Agile MEGA AMS-01 D0 LEP CDF BaBar CDF LPS Mark2 Pamela # of Channels [k] Accelerator GLAST Challenge Extensive CPU use Instrument Power 650 W: CAL 7,000 channels TKR channels ( < 200µW/ch ) Develop 9 ASICs Redundant readout Low-mass Cables

26 Conclusions The LAT is presently finishing up engineering model work and design engineering and is starting into flight-hardware production. The LAT is a large detector array with unprecedented channel count and computing power for a space-based experiment. The LAT will be our eye into the gamma-ray sky in the energy range from about 20 MeV to 500 GeV and will complement and work together with new ground based detectors sensitive only to higher energies. Working together with telescopes for all other wavelengths, GLAST will help to answer many puzzling questions in astrophysics and related particle physics by observing many of the most energetic and enigmatic objects in the universe. By using modern detector and computing technology, GLAST will greatly surpass the sensitivity of previous high-energy gamma-ray telescopes, providing us with exciting discovery potential. 26

27 log E (ev) 13 CAT CANGAROO WHIPPLE HEGRA VERITAS HESS MAGIC MILAGRO 11 CELESTE STACEE 9 EGRET AGILE GLAST 7 5 COMPTON HETE-2 INTEGRAL SWIFT year 27