1. Hiroyasu Tajima Stanford Linear Accelerator Center May 5, 2005 SLAC GLAST lunch talk Development of Next Generation Compton Gamma-ray Telescope

2. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 SGD Instrument Working Team H. Tajima, G. Madejski, T. Kamae KIPAC/Stanford Linear Accelerator Center T. Takahashi, K. Nakazawa Institute of Space and Astronautical Science/JAXA Y. Fukazawa Hiroshima University M. Kokubun, K. Makishima University of Tokyo Y. Terada RIKEN J. Kataoka Tokyo Institute of Technology M. Nomachi Osaka University M. Tashiro Saitama University

3. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Outline Concept. Science. Key features (requirements.) Instrument description.  Low noise front-end VLSI. Results.  Noise Performance.  Energy resolution.  Angular resolution, background rejection.  Polarization measurements.

4. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Sensitivity Gap… Sensitivity (MeV/cm 2 /s) No approved mission to cover 0.1–20 MeV energy band.  Sensitivity is mostly limited by BG. COMPTEL EGRET Astro-E2 GLAST OSSE INTEGRAL Next generation Compton telescope EXIST

5. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Multiple Compton Technique Proposed by T. Kamae et al. 1987  E1E1 E3E3 E2E2 11 22

6. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Science with Compton Telescope Wide Field-of-view (FOV)  All sky survey in soft gamma-ray band.  Time variability monitor. Supernovae (Nucleosynthesis) Flares (Blazars, AGNs, Solar corona). Gamma-ray bursts  New discovery. Narrow FOV  Low background, better sensitivity. Faint objects. Particle acceleration  Supernova remnants.  Galaxy clusters. Polarization. Compton telescope is not a dedicated polarimeter.

7. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Science Objectives Wide Field-of-view (FOV)  All sky survey in soft gamma-ray band.  Time variability monitor. Supernovae Flares (Blazars, AGNs, Solar corona). Gamma-ray burst  New discovery. Narrow FOV  Low background, better sensitivity. Faint objects. Particle acceleration  Supernova remnants.  Galaxy clusters. Polarization.

8. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Supernovae Science Nucleosynthesis of supernovae.  Nuclear gamma-ray lines.  Distinguish type Ia supernovae explosion models. 56 Ni distribution  light curve and/or line profile. Crucial for measurement of cosmic expansion acceleration. Deflagration model He-triggered detonation model Delayed-detonation model Velocity Time

9. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Expected Nuclear Lines from SNe Ia Delayed-detonation model Deflagration model Helium-triggered detonation model 56 Co (0.847, 1.238 MeV) 56 Ni (0.812 MeV) Expected 56 Ni and 56 Co nuclear lines from SNe Ia

10. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Active Galactic Nuclei (AGN) Unified scheme for AGN  Super-massive back holes (10 6 – 10 10 solar mass)  Different phenomenology is due to the orientation of jet with respect to the line of sight. Quasars, seyfert galaxies, radio galaxies and blazars. HST Image of M87 (1994)

11. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 AGN Spectra Synchrotron peak of TeV blazars peak at SGD bandpass.  High degree of polarization is expected. SSC model constraints (Synchrotron Self-Compton) J. Kataoka et al. 1998

12. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Gamma-Ray Bursts (GRB) Diverse time variability Short (0.4s) burst Double peaked 10 s 60 s ~100 s Multiple episodes Many short busrts in multiple episodes

13. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 GRB Properties Isotropic spatial distribution: cosmological origin. Two categories of GRBs: “long” and “short”.  Afterglow of “long” GRBs facilitates extensive studies in optical and radio band. Leading candidate: Hypernova  “Short” GRBs remain mystery.

14. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 GRB Science Constraints on GRB models.  Polarization measurement.  Gamma-ray production mechanism via multi-wave analysis. GLAST Fireball model prediction (Panaitescu 98) Compton Telescope

15. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Particle Accelerator in the Universe Strong electromagnetic field.  Neutron stars Shock acceleration.  Supernova remnants.  GRBs Large volume.  Galaxy clusters.

16. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Supernova Remnants RX J1713-3946: Candidate for proton acceleration.  GLAST can give definitive answer. Enomoto et al. Nature 416, 813 (2002) GLAST Compton telescope

17. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Galaxy Clusters Marginal evidence of non-thermal emission from Galaxy clusters in hard X-ray band.  Connection with the origin of UHECR?  AGN contamination Nevalainen 03 Combined spectrum for many clusters Rephaeli 04 Abel 2252 spectrum

18. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Polarization in Astrophysics Inverse Compton scattering.  Polarization depends on scattering angle or polarization of seed photons.  Geometrical information Synchrotron radiation.  Polarization is perpendicular to magnetic field direction.

19. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Key Features (Requirements) High energy resolution: ~ 1 keV (FWHM).  High angular resolution: ~ 1 o (FWHM).  High background rejection. Constraints from Compton kinematics. Low background: 10 -7 counts/cm 2 /s. Polarimetry. Low weight.  No heavy calorimeter. Wide energy band: 0.1–3 MeV. Large Field-of-View: > 2 sr. ~ 120 e – (RMS)

20. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Angular Resolution Doppler broadening will limit ultimate angular resolution.

21. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Semiconductor Multiple-Compton Telescope photo- absorption Compton Scattering pair- creation Si Detector CdTe Detector Si CdTe Doppler broadening is much smaller in Si.

22. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Wide FOV Instrument Concept Si+CdTe is essential for wide energy band.  Si: smaller Doppler broadening. Takahashi (ISAS) Si CdTe 40+40 layers of 0.5mm thick Si and CdTe, 4x4 array of identical modules 24cm

23. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Concept of Soft Gamma-ray Detector SGD aboard NeXT mission proposed at ISAS, Japan.  50 keV – 1 MeV  Narrow field of view.  Low background. Y. Suzuki (ISAS) 24 layers 0.5 mm thick

24. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Expected Performance of SGD Expected SGD spectra (100 ks) Large effective area (3300 cm 2 ) High background (5x10 -4 cm -2 s -1 keV -1 ) SGD SGD Effective area

25. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 SGD Polarization Sensitivity 5  detection limit: 3.2% @ 100mCrab 100 ks observation EE E’  Q = 66.0±0.4 %

26. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Energy Dependence of Sensitivity 40–500 keV Target selection

27. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Cygnus X-1 Hard state 5  limit Soft state 5  limit P = 2.99±0.54% (input: 2.5%) P = 1.23±0.24% (input: 1.2%) Hard state: small polarization expected. Soft state: large polarization expected.

28. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 GRB 021206 RHESSI Observation 80±20% P = 78±2% (input: 80%) P = 11±2% (input: 10%) 5  limit Coburn&Boggs 1 unit SGD w/o collimator Good timing resolution

29. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Technology Development Key R&D issues  Low noise electronics: collaboration with Ideas, Norway. Crucial for BG rejection by Compton kinematics: ~1 keV VA32TA, VA32TALP, VA64TA1 Low power (0.2mW/channel)  CdTe detector technologies. CdTe crystal Bump bonding  Compact packaging.

30. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 DSSD Energy Resolution EnergyResolution (FWHM) 13.9 keV1.1 keV 14.4 keV1.1 keV 60 keV1.3 keV 122 keV1.3 keV DSSD 2.56x2.56 cm 2 0.4mm pitch 0.3 mm thick Operation temperature -20 ~ 0 o C Fukazawa, et al. SPIE 2004 H. Tajima, et al. SPIE 2002

31. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 CdTe Energy Resolution CdTe pixel 1.6x1.6 cm 2 2x2mm 2 pitch 0.5 mm thick T. Mitani, et al. IEEE TNS 2004 S. Watanabe, et al. IEEE RSTD 2004, R4-3 0 o C 20 o C FWHM 1.7 keV

32. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 BGO Readout by APD T. Ikagawa, et al. NIM 2004 HPK S8664-1010N 1.0x1.0 cm 2 BGO 1.0x1.0x1.0 cm 3 BGO 30.0x4.8x0.3 cm 3 -20 o C -15 o C Minimum detectable Energy: 11 keV

33. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Compton Reconstruction 22 Na, 511keV events Stack of 6 DSSDs 3 CdTe detectors obtained with the first prototype Two 57 Co, 122keV events Operated at ~ -5 o C S. Watanabe, et al. IEEE RSTD 2004, R4-3 Before Compton constraint After Compton constraint  E/E ~ 3%

34. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Angular Resolution Scattering angle resolution @ 122 keV Experimental angular resolution is dominated by Doppler broadening. Energy resolution Strip size Good enough Fukazawa et al., SPIE 2004 Tanaka et al., SPIE 2004 Energy dependence

35. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Polarization Measurement @SPring-8 177 keV polarized photon EGS4.4 MC Azimuth Scattering Angle (deg) CdTe pixel detector DSSD CdTe 10mm Si Good agreement between data and MC DATA 177 keV polarized photon  43±3 % 41±2 % Mitani et al., IEEE NSS 2003

36. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 Conclusions and Future Prospects Good energy resolution is achieved.  VA64TA (low noise, low power, close to final design) is out of fab. CdTe technologies are getting mature.  Uniform CdTe properties. (K. Onuki et al. SPIE 2004)  Good bump bonding yield. Compton reconstruction demonstrated.  Angular resolution.  Polarization. R&D still required.  Compact packaging.  2D VA128TA  Thick CdTe detectors. 4x4 cm 2 DSSD stack with readout electrode on the side (ISAS/MHI)

37. Next Generation Compton Telescope, H. Tajima,GLAST lunch, MAY 5, 2005 NeXT Mission Road Map 2004/Jan: ISAS science committee selected NeXT over VSOP-2 for next science mission. (Engineering committee selected Solar sail.) 2004/Aug: ISAS/JAXA decided not to make decision on next mission. 2005/Mar: ISAS/JAXA calls for next mission proposals. (NeXT, VSOP-2, Solar sail will likely be accepted for prephase-A study.) 2005/Sep: Submission of final mission proposals. 2006/Jan: Selection of the next mission. 2006/Apr: Phase-A study. 2007/Apr: Start Proto-model fabrication.