(Krause 2004)Steven BoggsUC BerkeleyDepartment of Physics

MeV Gamma Ray Nuclear Astrophysics

Yesterday: Science and ObservationsToday: Instrumentation

Nuclear Gamma-Rays

Atmosphere is opaque at these energies.

Gamma-ray interactions

Index of refraction ~1.0000

Penetration ≥ cm into materials

Standard mirrors & lenses don’t work

CZT Semiconductor

Liquid Xe

Si Semiconductor

Ge Semiconductor

Gamma Ray Detectors

NaI, CsI, BGO

Scintillators• high Z• large volume• room temperature• moderate/poor resolution (3-10%)

Solid State• good/excellent resolution (<2%)• may require cooling• finer position resolution• more channels/power

The radiation environment

The Space Radiation EnvironmentThe Space Radiation Environment

Secondaries induced by cosmic-ray

interaction with upper atmosphere:

Albedo photons, neutrons, electrons,

positrons

Radiation belts:

Trapped protons (SAA) & resulting activation, electrons

Cosmic rays:• Photons• Protons (& activation)

• Alphas• Ions• Electrons• Positrons

Sun through solar flares: photons, charged particles

Compton Gamma-Ray Observatory(1991-2000)

COMPTEL (0.8-30 MeV)

EGRET(20 MeV – 30 GeV)

BATSE(20-600 keV)

OSSE(50 keV – 10 MeV)

Spectroscopy, no Imaging

“light bucket”

Galactic Center Positrons

(Purcell et al., 1993)

(from P. von Ballmoos)

Coded Aperture Imaging

pinhole camera…. with lots of pinholes

Good for: point sources photons that stop in the mask (<0.2 MeV)

IBIS (15 keV-10 MeV)

JEM-X(3-35 keV)

SPI(30 keV-8 MeV)

OMC(500-600 nm)

INTErnational Gamma-Ray Astrophysics Laboratory (launched October 2002)

E/E ~ 500, ~ 2º

E/E ~ 10, ~ 20’

IBIS/INTEGRAL

ISGRI: 128x128 CdTe array (4x4x2 mm3)PICsIT: 64x64 CsI array (8.4x8.4x30 mm3)

IBIS Galactic Plane Survey

(Bird & Walter 2004)

SPI/INTEGRAL

19 Ge detectors

(Weidenspointner et al., 2008)

SPI Positron Map

Compton Gamma-Ray Observatory (1991-2000)

COMPTEL (0.8-30 MeV)

EGRET(20 MeV – 30 GeV)

BATSE(20-600 keV)

OSSE(50 keV – 10 MeV)

(Schoenfelder et al., 1993, ApJS 86, 657)

COMPTEL DetectorsD1: 4188 cm2 liq. scint.D2: 8620 cm2 NaIE: 5-8% (FWHM)X ~ Y ~ 2 cm (1)Z ~ 3 cm (1)t ~ 0.25ns

COMPTEL Performance0.8-30 MeVE/E ~ 9-14 (FWHM) ~3º

Aeff < 20 cm2

FOV ~ 1str

COMPTEL - Compton Imaging cos = 1+mc2(1/E2-1/E)

26Al (1.809 MeV), ~1Myr

(Oberlack et al., 1996; Pluschke et al., 2001)

Compton Telescopes: Then & Now

CGRO/COMPTEL• ~40 cm3 resolution• E/E ~ 10%• 0.1% efficiency

ACT Enabling Detectors• 1 mm3 resolution• E/E ~ 0.2-1%• 10-20% efficiency• background rejection• polarization

3 decades…

Overview of the Overview of the Nuclear Compton TelescopeNuclear Compton Telescope

A balloon-borne A balloon-borne -ray spectrometer, polarimeter & imager-ray spectrometer, polarimeter & imager

Steven Boggs, UCBNCT Collaboration: Berkeley, NTHU, NCU, NSPO, NUU, LBNL, CESR

Heart of NCT:Cross Strip 3-D GeDs • 37x37 strips• 2-mm pitch• 15-mm thickness• 81000 mm3 volume• 1.6 mm3 localization• ~2.1-keV noise resolution

Nuclear Compton Telescopeballoon payload

3D GeD Design

(Luke et al. 1992, 1994)

Single-Pixel Spectra (56Co)• excellent GeD Spectroscopy• plus full 3-D positioning

60Co Laboratory Tests1.173, 1.333 MeV

1.173 MeV processed image

Source Decay Energy Goal SNe Ia (?) e+e- 0.511 36 map SNe II/Ib 26Al 1.809 MeV 36 map 60Fe 1.173, 1.333 5 detect SNe 44Ti 1.157 resolved line BHs e+e- ≤0.511 discovery

Next flight, May 2009• northern hemisphere• primarily compact objects

The 2005 balloon flight from Fort The 2005 balloon flight from Fort SumnerSumnerImpressions from the NCT 2009 Balloon flightImpressions from the NCT 2009 Balloon flight

BGO shieldBGO shield

lNlN22 dewar dewar

Pre-AmpsPre-Amps

Differential Differential GPSGPS

RotorRotor

DetectorDetector

Electronics BayElectronics Bay

CSBF SIPCSBF SIP

Solar PanelsSolar Panels

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4D sin = n

Alternate layers of high/low Z materialsex. W/Si

D ~ 25 Å (technological limit) < 1 Å (0.18 Å @ 68 keV)~ 30’f ~ 10 m

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SN 1987A in the LMC

(Suntzeff et al.1992; Diehl & Timmes 1998)

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Blue supergiant (~20 M, 6 M He core) (Arnett et al., 1989)

Spherical models predict 44Ti < 1000 km/s

56Ni mixed out to ~3000 km/s (0.7 keV at 68 keV)

(Motizuki & Kumagai 2004)

~110-4 M

2D sin = n

Use a crystal to bend (“focus”) the -rays

D ~ 1 Å (crystal spacing) < 1 Å (0.014 Å @ 0.847 MeV) ~ 10’f ~ 60 m

Bragg Scattering

von Ballmoos et al., CESR, Toulouse

Laue Lens: Focusing -rays