Thenext Frontier in Gamma-Ray Astronomy: Development of Detectors for ... · SLAC - AIS, 2 Sept 2009 ThenextFrontier in Gamma-Ray Astronomy: Development of Detectors for the MeV range

SLAC - AIS, 2 Sept 2009

The next Frontier in Gamma-Ray Astronomy:

Development of Detectors for the MeV range ~0.1 – 100 MeV

Gottfried KanbachMax-Planck-Institut für extraterrestrische Physik, Garching, Germany


The electromagnetic spectrum and the transparency of Earth’s atmosphere

Energy

Č

Satellite Telescopes


Past: Compton Gamma-Ray Observatory (1991-2000)

OSSE

COMPTEL EGRET

BATSE

0.01 0.1 1 10 100 1000 10000 MeVBATSE,OSSE COMPTEL EGRET

CGRO


COMPTEL, 1-30 MeV

EGRET, >100 MeV


Galactic γ-ray line emission511 keVFWHM 2.95 keV

P. Jean et al.

R. Diehl et al.

26Al, 1809 keVFWHM 3.1 keV


Present: Fermi Gamma-Ray Space Telescope (2008 - )

0.01 0.1 1 10 100 1000 10000 MeVFermi LAT

CGRO


The‚MeV‘ gap !

Situation of multi-wavelength High-Energy Astronomy: Severe sensitivity deficit at MeV energies

FERMI-LAT


COMPTEL, 1-30 MeV

Toscanelli's World Map, 1474

Fermi 3 mo. sky survey>100 MeV

also:Air Cerenkov Telescopes

HESS, Veritas, Magic

ROSAT PSPC0.1-2 keV

also: SWIFT, INTEGRAL

coming: NuStar, Astro-H

the gamma-raymainland:~50 Mev to ~TeV

the X-ray continent:~100 ev to ~100 keV

the MeV continent

Future ???


Astrophysics in the ‚MeV‘ regionMeV300

100

30

10

3

1

0.3

0.1

nuclear binding energy~ 8 MeV

„the starting line of acceleration...“

electron restmass 0.511 MeV

Nuclear Processes cosmic accelerators

non-thermal continuum(Bremsstrahlung, synchro-cyclotron radiation,

inverse Compton,...)

nuclear γ-lines


Astrophysics in the ‚MeV‘ regionMeV300

100

30

10

3

1

0.3

0.1

Nuclear processes& Nucleosynthesis

cosmic accelerators

511 keV: novae; solar flares;GC sources

galactic radioactivity 26Al; 60Fe, CRs & ISMSNeyoung SNRs 44Ti

stellar & solar nuclear reactionsSED maxima of manyFermi/COMPTEL Blazars

non-thermal spectrain black-hole binaries,micro-quasars

GRB: spectra & polarization

Fermi LAT sources: pulsars, unids,binaries, AGN, etc.

Galactic and extragalacticdiffuse background

nuclear resonance absorption


• photon interaction cross-sections gothrough a minimum

• double Compton scattering efficiencies low• Compton event reconstruction incomplete

and limited by Doppler broadening• Pair events limited by nuclear recoil

• Instrumental background in space isstrong

Why is the sensitivity in theMeV region so low?


Compton Scattering (0.2-10 MeV)Photon Crossection MinimumScattered photons with long rangeTelescope:Compton Camera Coincidence System

Pair Creation (> 10 MeV)Photons completelyconverted to e+e-

Telescope:Tracking chambersto visualize the pairs

CrossSection

Energy

Photoeffect(< 100 keV)

Photons effectivelyblocked and stopped

Telescopes:

CollimatorsCoded Mask Systems

Detection of Gamma Radiation


COMPTEL, 1-30 MeV

COMPTEL

Trigger: t.o.f. delayed coincidence


Schematics to illustrate COMPTEL instrumental background events


Effective Area and Sensitivity

Source: Ns = A T ∫ Isrc(E) ε(E) dE

Background: Nb = A T ∫ Isky(E) ε(E) dE + Ninst

Significance: nσ = Ns / √ Nb

Detection threshold:

Fthresh =nσ √ Nb

A ε T ΔE

Instrumental Background:~ 100 keV bis ~ 10 MeV


MeV Telescope RequirementsImprove:

sensitivity (reduce background), field of view, angular resolution Imaging

effective area (= count rates) Timing

energy resolution over large E rangeSpectroscopy

control detector systematics Polarimetry


Imaging, Timing, Spectroscopy, Polarimetry

• Mapping the Sky:deep, continuous, survey from ~0.3-100 MeVDiffuse and localized sources

• Variabilityfast: GRBs, transients, SGRs, Novae

solar flares, pulsars (periodic)slow: AGN, SNe

• Broadband spectra:SED characteristic for particles, fields & geometry

• Narrowband spectra:Cosmic radioactivity with short and long half-livesNuclear resonance absorption

• Polarization: Pulsars, GRBs, AGN


MeV Telescope Concepts

Classical Compton Event Circles

(no electron tracking)

Compton arcs for events with electron track or 3rd

interaction

Direct imaging of pair-creation events

Detectors using Compton Scattering and Pair CreationCOMPTEL, EGRET, LAT

Collimated Detectors: OSSE, RHESSI, ASTRO-H

Coded Mask Systems:INTEGRAL, SWIFT

Laue Lens Telescope:DUAL

20-50m


MPE Developments 1996-2004:The Medium Energy Gamma-Ray Astronomy

Project MEGA


Proof of principle:The MEGA Compton/Pair

telescope prototype

Tracker: double sided

Si strip detectors

Calorimeter: 2(3)D resolving

CsI/PIN diodevoxel array

Compton Scattering:


Prototype and Full-size Instrument(GEANT models, status 2001)

30 layers of Si strip detectors36 x 36 cm2 , 0.5 mm thick

Full CsI Calorimeter

~10 layers of Si strip detectors20 calorimeter modules


Prototype Tracker: 11 layers with 3x3 SSDs (ea. 6x6cm2, 470μm pitch)Total Si area ~ 4000 cm2, ΔEFWHM: > 15 keV @ 122 keV

Calorimeter: 20 modules of 120 CsI(Tl) bars each, 5x5x[20,40,80] mm3

PIN diode readout (Hamamatsu), ΔEFWHM : > 70 keV @ 662 keVΩ fill factor lower hemisphere ~ 40%

Aeff estimate :

Aeff = (1-e-μd ) Ageomη= 16 cm2 η

with η = 0.4 x 0.3Aeff ~ 2 cm2


Tracker:11 layers, 8448 strips

Calorimeter:20 blocks, 2400 crystals


Layout of the MEGA double sided Si strip detectors

Design: MPE HLL (Semiconductor Lab. of MPE, Garching)Fabrication: Eurisys, Strasbourg, FranceRef: Bloser et al., NIM, 512, 228 (2003)

• wafers: 6x6x0.5 cm3 ; 128x128 strips• n-side strips separated by p-spray implantation• AC coupling: Al strips on an insulating layer• Punch-through bias between strips and common bias ring• Multiple guard rings on p-side

p-sidelayout


3x3 wafers mounted on grid structure (PEEK frame)

Shadow of 6mm Pb mask irradiated with 57Co

Resolution of tracker measured with muons: 290µm

ΔEFWHM: ~ 15 keV

18 cm


Calorimeter Modules• 120 CsI crystal bars 0.5x 0.5x [2, 4 , 8] cm3 / module• Monolithic 10 x 12 PIN Diode Array with 5x5 mm2 pixels

(Hamamatsu)• R/O electronics integrated on the backside of the Hybrids.• Energy resolution @ 662 keV: ~ 10 % FWHM (3-D)• Spatial resolution: x-y: pixel size; z:~1.5 cm


Calibration of MEGA: Free Electron Laser, Inverse Compton Beam

(HIγS FELL, Duke U., NC) 2003

injection from Linac@ 270 MeV

;4)(1

4;

2;

)2/1(2;

22

2

2

2

2

cmE

EE

cmeBK

KhcE

cmE

e

ph

ph

e

www

wwph

e

e

γγθ

γπλ

λγγ γ

++≅=

+==

electron laser photon energy IC gamma-rayenergy (UV-IR) energy

RF cavity

wiggler mirror

e--bunch 1

e--bunch 2 laser pulse 1

γ-ray beamE-vector horizontal

0.7–50 MeV

mirror


Angular resolution in the Compton range

0.05.0

10.015.020.0

100 1000 10000

Energy [keV]

Angu

lar r

esol

utio

n as

FW

HM

of A

RM

[deg

]

Tracked Not tracked

2 MeV 5 MeV 8 MeV

Increase due to incomplete absorption (electron escapes, secondary photon leaks)

20°

Width of angular resolutiondominated by energy resolution in calorimeters (e.g. 8 cm calorimeters: 15% - 22%) and notby physical limits!

Doppler-broadening: ~0.23° at 2 MeV in Silicon


Angular resolution in the Pair creation range12 MeV 25 MeV 49 MeV

Increased influence of Molière-scattering and of unknown recoil of nucleus

20°

Angular dispersion as 68% containment radius around known source position

0

5

10

15

20

10 100Energy [MeV]

Ang

ular

di

sper

sion

[deg

]

MEGA

EGRET

The angular resolutionof the MEGA prototypeat 49 MeV is 2x better

than EGRET!


MEGA Prototype field of view @ 50 MeV: calibration beams to ~80° off-axis


⎟⎟⎠

⎞⎜⎜⎝

⎛−+⎟⎟

⎠

⎞⎜⎜⎝

⎛=

Ω∂∂ χϕσ 22

22

cossin22 g

i

i

g

i

ge

EE

EE

EEr

Azimuthal distribution: a*cos(2(χ+χ0))+c

Azimuthal scatter angle χ

Beam100% polarized

E

Polarization: Measurement & Simulation

Data

Simulation

MEGA Calibration result:E Modulation [%](MeV) meas. sim.0.7 17± 4 19± 12.0 13± 3 14± 15.0 6± 3 3± 2


… after MEGA was proposed as a German Small Satellite project (2nd place in 2001), and a balloon flight of the prototype could not be realized, the project was discontinued in 2003 by the MPE directorate.

… since 2005 we started to discuss a renewed effortfor a MeV mission, based on

• new central science cases (among others: nucl.resonance absorption in high-z GRBs, low energy follow up for Fermi sources)

• new detector technology: scintillators, sensors, electronics, simulations

• ESA cosmic vision announcement


GRIPSGRB Investigation via Polarisation and Spectroscopy

The GRIPS-GRM Simulation Model

Tracker: Double-sided Si-strip detectors

50 kg Silicon, 64 layers with 8x8 wafers (10x10x0.05 cm3), 500 μm pitch, 2.5 keV FWHM energy resolution, 10 keV trigger threshold

Calorimeter: LaBr3

500 kg, 0.5x0.5x2/4/8 cm, 4.4% energy resolution (FWHM) @ 662 keV, 0.5 cm depth resolution in 8 cm crystals, 30 keV trigger threshold

ACS: Plastic scintillator

120 kg BC408, 50 keV average veto threshold

166 cm

Tracker: Double-Sided Si-strip detectors

Calorimeter: LaBr2 with SDD readout

ACS: plastic scintillator

http://www.grips-mission.euGreiner et al., 2009, Exp Astron. 23, 91Zoglauer et al., 2008, New Astron. Rev. 52, 431


yesyesyesnoyesHygroscopic

?138La decay

138La decay

nonointrinsicradioactivity

371350370560415peak emissionwavelength, nm

~3.6%~2.0%2.6%~7%5.6%energy resolution(FWHM, 662 keV)

~17~25~25~2000~200decay time, ns

6850685440scint.light yield, photons/keV

5.23.795.294.513.67density, g cm-3

CeBr3LaCl3(Ce)LaBr3(Ce)CsI(Tl)NaI(Tl)Scintillator

Investigations of a Calorimeter with improvedenergy resolution and fast timing: old and new Scintillators


Silicon Drift Detector

scintillation lightAGADE Workshop, 2-5 June 2008 Bernhard Huber, MPE, email: [email protected]


Scintillators & Test setup

AGADE Workshop, 2-5 June 2008 Bernhard Huber, MPE, email: [email protected]

CsI(Tl) LaBr3:Ce

CeBr3

scintillator

SDD

case

light guide

cold finger


Energy spectrum of 137Cs measured with LaBr3(Ce) and UV sensitive PMT:resolution at 662 keV ~3.2% (FWHM) (credit: V. Bogomolov, MSU)


Timing resolution between various scintillators(credit: D. Kolitzus, B. Huber, MPE)

PMT / Scint

radioactive source22Na, 60Co…

194 ± 2LaBr3 vs. CeBr3

182 ± 3BaF2 vs. CeBr3

134 ± 2BaF2 vs. LaBr3

139 ± 2BaF2 vs. BaF2

timingresolution(ps) FWHM

crystals used


Simulations of GRIPS-GRM:(credit: A. Zoglauer, UCB)

events & background :MGGPOD (Weidenspointner et al., 2005)

reconstruction & instrument fct.MEGALib(Zoglauer, et al., 2006)

Mission:equatorial LEOzenith scanning


Resolutions and Effective Area

Imaging mode event selections are chosen to optimize the narrow-line point-source sensitivity of the telescope including earth horizon cuts, Compton scatter angle cuts, etc.

(Zoglauer et al, 2008)



Minimum Detectable Polarization for typical GRB spectra


GRIPS

GRIPS as a nuclear lineimager/spectrometer

(Zoglauer et al, 2008)


GRIPS continuum sensitivity: observation time 106 s, ΔE = E


GRIPS sensitivity in context


Number of sources that can be detected with the sensitivity of GRIPS

(1 yr exposure) (5 yrs exposure)

Type # total # new

GRBs 660 3300 3300

Blazars 820 950 300

Other AGN 250 300 0?

Pulsars/AXP 60 90 0?

Unidentified 170 230 60

Based on extrapolations of KNOWN source spectra!


GRIPS (5 years): based on simulated Fermi catalogue.

Effectively based on EGRET sources!


GRIPS Galctic bulge 511 keV modelled with a …

smooth and

source distribution


Summary

GRIPS would be a major step forward in nuclear line science, especially all-sky imaging!

GRIPS can be ready for the next ESA Cosmic Vision AO

GRIPS could be a huge leap forward in MeV astronomy for GRBs, cosmic radio-activity, and high-energy sources


The End


GRIPS Photopeak energy resolution


GRIPS γ-line field of view


How to find high-redshift GRBs?Due to characteristic spectrum of GRB Afterglow:

– Photometry in optical: up to z~6– Photometry in NIR: up to z~12-14 (GROND)– Beyond z~14: not feasible from ground in gamma-rays?!

MISTICI (2005)

z=6.29


Nuclear Resonance photon absorption ● PDR – Pygmy resonance: produced by the resonance capture of photons on nuclear levels with E of ~ 3-9 MeV

(Axel 1962; Hayward 1977; Van Isacker et al. 1992)

● GDR – Giant Dipole Resonance: process that is crudely described as oscillation of the neutron fluid relative to protons ( not in H, only above He) ~15-25 MeV

(Goldhaber and Teller 1948; Ahrens 1985; Eramzyan et al. 1986)

● Delta-resonance – absorption of photons with an energy ~325 MeV by a nuclei via formation of the Delta-isobar, that leaves a target nuclei and pi-meson(s) in the exit channel (Ahrens 1985; Hagiwara et al. 2002)


Jochen GreinerFriedrichshafen, 28.5.2008

Interactions of Photons and Atomic Nuclei Interactions of Photons and Atomic Nuclei

We See Effects of (with increasing energy):Excitation of Single Nucleons in Nucleus Potential ("Nuclear Lines")

– hν=Enucl

Collective Excitations of Nucleon Groups ("Pygmi/Giant Resonances")– giant resonances: protons versus neutrons– quasi-deuteron resonances: a pair of proton and neutron– each of these occur in all multipole orders

Excitations of Single Nucleons ("Delta Resonance")…-> Hadron/Quark Phase Transitions



Resonance absorption: the effectResonance absorption: the effect

NHfgd=5x1022 cm-2

NHintr=1028 cm-2

z=0

Z=1 (solar)

NHfgd=5x1022 cm-2

NHintr=1028 cm-2

z=0

Z=0.6

NHfgd=1025 cm-2

NHintr=1025 cm-2

z=0

Z=1 (solar)

NHfgd=5x1022 cm-2

NHintr=1028 cm-2

z=0

Z=0.1



The brightest COMPTEL/EGRET GRB: The brightest COMPTEL/EGRET GRB: 11σσ result for GRB 930131result for GRB 930131

DR @ z~0.65

Data of Sommer et al. (1994); Ryan et al. (1994); Bromm & Schaefer (1999)

GD

R @

z~0

.65

(Iyudin et al 2005)

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Thenext Frontier in Gamma-Ray Astronomy: Development of Detectors for ... · SLAC - AIS, 2 Sept 2009 ThenextFrontier in Gamma-Ray Astronomy: Development of Detectors for the MeV range