Achievements of the ASTROE Hard XRay Detector Development

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Achievements of the ASTRO-E Hard X-Ray Detector
Development
420mm

• Makoto TASHIRO (Saitama Univ.)
• K. Makishiama, M. Kokbun (Univ. Tokyo),
• T. Kamae, T. Mizuno (SLAC),
• T. Takahashi, T. Murakami, K. Nakazawa (ISAS),
• Y. Fukazawa (Hiroshima Univ.), K. Yamaoka (RIKEN)
• and the HXD team

186 kg
HXD-S
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ASTRO-E and the HXD
ASTRO-E Japanese 5th X-ray satellite XRT 1500
cm2 (by 5 units at 6 keV) XIS 0.4-10keV Imaging
Spec. XRS 0.4-10keV Spectroscopy
(dE 12eV!) with 32pixel imaging HXD
10-600keV spectroscopy
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ASTRO-E was lost due to a trouble of 1st stage
of rocket February 10, 2000

• ASTRO-E2 (recovery mission) has been approved to
  be launched in February, 2005
• The HXD team now starts to produce HXD-II
• which should be supplied in spring 2003

the new logo
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The Hard X-ray Detector

• Combination of a Well-type phoswich counter and a
  Si PIN diode
• The BGO Well acts as an active collimator as well
  as an active shield
• By placing the Well-units in a matrix, each unit
  acts as an active shield of each other
• Energy range 10-600keV
• Effective Area
• 160cm2 at 20keV,
• 330cm2 at 100keV.

PIN diodes
Top View
photons
Well-type Phoswich counter
decay time GSO 122 ns BGO 706 ns (_at_
-20deg)
Well type counters
Side View
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Signal Processing in the WPU
decay time GSO 122 ns BGO 706 ns (_at_
-20deg)

• Well unit
• Anode
• (for GSO trigger)
• Dynode
• (for GSO spectrum)
• 4 PINs
• Hardwired Event Selection
• Pulse Shape Discrimination

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The Data Flow in HXD

• All WPU/TPU are connected to the backplane of
  the AE-box. To reject all the Compton events in
  the HXD, it is important for each unit to be
  informed of the hit pattern of the other 35
  units.
• Digital Electronics, equipped with CPUs, handles
  all kind of scientific data. Installed software
  has a capability to reduce less important data in
  order to save telemetry band width.

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DE data selection

• Hit pattern selection
• Any patterns are able to choose by command
• Pulse Shape Discriminator
• For more flexible discrimination in orbits
• Trigger pattern selection
• PIN triggered or GSO triggered
• Analog signal processing status flag
• A/D conversion flag, PSD flag, UD/ LD flags
• short time interval discrimination
• To reject a possible train of events induced by a
  large energy deposit by protons

• The DE provides
• diagnostic data from sensors.
• Background monitor
• Radiation belt monitor
• GRB software detection

Sufficient process speed
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The Background Spectrum at Sea Level
Total spectrum
1281646 counts
PSD Selected spectrum
34308 counts
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Spectrum of Line Gamma-rays

• Energy resolutions
• PIN
• 3.60.1 keV_at_ 22keV
• 3.50.1keV _at_ 41keV
• GSO
• 30.50.6 _at_ 41keV
• 10.60.5 _at_ 511keV

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Expected Sensitivity in Orbit

• 3s significance calculated from the expected
  background in orbit

Continuum Components
Line Components
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Possible improvements from HXD to HXD-II (for
ASTRO-E2)

• HXD-AE
• No major changes
• HXD-DE
• No change in hardware
• Small changes in software

• HXD-S (sensor)
• Extension of effective area of PIN diode (by
  reducing N stop area) 20 up
• Improvement of front electronics configuration
• Bias voltage 400V-gt 500V
• Reduce radio isotopes in sensor materials
• 0.5mmt CdTe ?

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Summary

• The performance of the flight model HXD was
  verified, and we confirmed that the background
  level of both the phoswich counters and PIN
  doides at sea level is in the lowest level we
  have reached through out our development.
• The expected sensitivity in orbit was calculated
  based on the results, and HXD is expected to have
  the highest sensitivity in the energy range of
  10-300 keV.
• We also obtained the spectrum from line g-rays
  and confirmed that the 31 keV line can be clearly
  detected.
• Considering charged particles, we did careful
  design on the front-end electronics, and
  succeeded in reducing the recovery time much
  shorter than the original value and verified
  enough speed of the onboard data processing. We
  verified the stability using the flight model
  electronics, and confirmed that our system will
  maintain its performance within the expected
  counting rate in space.
• Based on these achievements of the previous HXD
  development, we now started to produce HXD-II for
  the recovery mission ASTRO-E2, that would be an
  unique and excellent mission with the wide band
  X-ray spectroscopy capability.