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MeV Gamma Ray Nuclear Astrophysics Yesterday: Science and Observations Today: Instrumentation. (Krause 2004). Steven Boggs UC Berkeley Department of Physics. Nuclear Gamma-Rays. Atmosphere is opaque at these energies. Gamma-ray interactions. Index of refraction ~1.0000

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slide1

MeV Gamma Ray Nuclear Astrophysics

Yesterday: Science and Observations

Today: Instrumentation

(Krause 2004)

Steven Boggs

UC Berkeley

Department of Physics

slide2

Nuclear Gamma-Rays

Atmosphere is opaque at these energies.

gamma ray interactions

Gamma-ray interactions

Index of refraction ~1.0000

Penetration ≥ cm into materials

Standard mirrors & lenses don’t work

slide4

Gamma Ray Detectors

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

Liquid Xe

NaI, CsI, BGO

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

Si Semiconductor

CZT Semiconductor

Ge Semiconductor

the radiation environment

The Space Radiation Environment

Sun through solar flares: photons, charged particles

Radiation belts:

Trapped protons (SAA) & resulting activation, electrons

  • Cosmic rays:
    • Photons
    • Protons (& activation)
    • Alphas
    • Ions
    • Electrons
    • Positrons

Secondaries induced by cosmic-ray interaction with upper atmosphere:

Albedo photons, neutrons, electrons, positrons

The radiation environment
slide7

Compton Gamma-Ray Observatory

(1991-2000)

COMPTEL

(0.8-30 MeV)

OSSE

(50 keV – 10 MeV)

BATSE

(20-600 keV)

EGRET

(20 MeV – 30 GeV)

slide8

Spectroscopy, no Imaging

“light bucket”

Galactic Center Positrons

(Purcell et al., 1993)

slide10

Coded Aperture Imaging

pinhole camera….

with lots of pinholes

  • Good for:
  • point sources
  • photons that stop in the mask (<0.2 MeV)
slide11

INTErnational Gamma-Ray Astrophysics Laboratory (launched October 2002)

IBIS

(15 keV-10 MeV)

JEM-X

(3-35 keV)

E/DE ~ 10, Df ~ 20’

E/DE ~ 500, Df ~ 2º

SPI

(30 keV-8 MeV)

OMC

(500-600 nm)

slide12

IBIS/INTEGRAL

ISGRI: 128x128 CdTe array (4x4x2 mm3)

PICsIT: 64x64 CsI array (8.4x8.4x30 mm3)

ibis galactic plane survey

IBIS Galactic Plane Survey

(Bird & Walter 2004)

slide14

SPI/INTEGRAL

19 Ge detectors

slide15

SPI Positron Map

(Weidenspointner et al., 2008)

slide16

Compton Gamma-Ray Observatory (1991-2000)

COMPTEL

(0.8-30 MeV)

OSSE

(50 keV – 10 MeV)

BATSE

(20-600 keV)

EGRET

(20 MeV – 30 GeV)

slide17

COMPTEL - Compton Imaging

cos  = 1+mc2(1/E2-1/E)

COMPTEL Detectors

D1: 4188 cm2 liq. scint.

D2: 8620 cm2 NaI

DE: 5-8% (FWHM)

DX ~ DY ~ 2 cm (1s)

DZ ~ 3 cm (1s)

Dt ~ 0.25ns

COMPTEL Performance

0.8-30 MeV

E/DE ~ 9-14 (FWHM)

Df ~3º

Aeff < 20 cm2

FOV ~ 1str

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

slide18

26Al (1.809 MeV), ~1Myr

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

slide19

Compton Telescopes: Then & Now

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

3 decades…

  • CGRO/COMPTEL
  • ~40 cm3 resolution
  • DE/E ~ 10%
  • 0.1% efficiency
slide20

Overview of the Nuclear Compton Telescope

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

Steven Boggs, UCB

NCT Collaboration: Berkeley, NTHU, NCU, NSPO, NUU, LBNL, CESR

slide21

Nuclear Compton Telescope

balloon payload

  • 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
slide22

3D GeD Design

(Luke et al. 1992, 1994)

slide23

Single-Pixel Spectra (56Co)

  • excellent GeD Spectroscopy
  • plus full 3-D positioning
slide25

60Co Laboratory Tests

1.173, 1.333 MeV

1.173 MeV processed image

slide26

Next flight, May 2009

  • northern hemisphere
  • primarily compact objects
slide27

The 2005 balloon flight from Fort Sumner

Impressions from the NCT 2009 Balloon flight

slide29

BGO shield

Pre-Amps

lN2 dewar

slide31

Rotor

Differential GPS

Solar Panels

Electronics Bay

Detector

CSBF SIP

slide34

4D sin  = n 

  • Alternate layers of high/low Z materials
  • ex. W/Si
  • D ~ 25 Å (technological limit)
  • < 1 Å (0.18 Å @ 68 keV)
  • ~ 30’

f ~ 10 m

slide38

SN 1987A in the LMC

~110-4 M

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

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)

slide39

Bragg Scattering

  • 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

slide40

Laue Lens: Focusing g-rays

von Ballmoos et al., CESR, Toulouse

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