J. Kataoka , Y.
Yatsu, T. Ikagawa, T. Saito, Y. Kuramoto,
N. Kawai, J. Kotoku (Tokyo Tech)
Y. Ishikawa, and N. Kawabata (Hamamatsu Photonics K.K.)
Abstract: We report the recent progress of
avalanche photodiodes
(APDs)
produced by Hamamatsu Photonics,
as an excellent low-energy
X-rays and g-rays
detector. The best FWHM energy resolutions of 9.4 % and 4.9 % were
obtained for 59.6 keV and
662 keV g-rays respectively,
as measured with the CsI(Tl) crystal. We have achieved the energy resolution of 6.4 % for direct illumination of APDs with
5.9 keV X-rays.
We present various applications of using APDs for
future space space researches
and nuclear medicine. In particular 2-dim APD array will be a
promising device for a wide-band X-ray and g-ray
imaging detector.
1: introduction to the APD
4: application to “Tokyo Tech satellites”
CCD
Performance of the
most recent avalanche photodiodes
for future
X-ray and gamma-ray Astronomy
+
hn
+
-
p＋
n+
n-
n
p
e→
E
Avalanche
Region
-
1cm APD
≈ 1 inch PMT
for
the light collection
APD
PMT
Producing
an internal gain of G > 50, which improves S/N significantly
High
quantum efficiency of h > 80% at
l= 500-800 nm
The good features of both PDs and PMTs are shared by APD!
2: Performance as a scintillation photon detector
APD
(4.9%FWHM)
PMT
(5.9%FWHM)
662 keV
59.5 keV
APD
(9.4%FWHM)
PD
(29%FWHM)
PMT
vs APD (@662 keV)
Measured with
1cm3 CsI(Tl)
CsI(Tl) ….. 4.9 %(APD) vs 5.9 %(PMT)
GSO ….. 7.8 %(APD) vs 9.3 %(PMT)
BGO ….. 8.3 %(APD) vs 10.4 %(PMT)
PMT vs PD (with CsI(Tl))
59.5 keV … 9.4%(APD) vs
29.0%(PD)
122 keV … 7.4%(APD) vs
16.9%(PD)
Energy resolutions
are much better
than those with
PMTs & PDs!
Moreover, Eth is as low as 5 keV @room temperature!
~5 keV
3: Performance as a soft X-ray detector
8keV X-ray
241Am
59.5
keV
Thanks to the strong electric field in the device, E = 3x107 V/m,
carriers can be collected within t ~ 1.9ns
perfect counting performance up to ~ 108 cts/s!
Energy resolution is about DE ~ 380 eV (FWHM, @ 0 deg), meaning
that APD can work as an excellent soft-X ray spectrometer
CUTE-1:
successfully
launched in 2003
10x10x10 cm3, 1kg
CUTE-1.7:
scheduled in 2005
10x10x20 cm3, 2kg
Hu-ring:
scheduled in 2008-
50x50x50 cm3, 50kg
GRB satellite
Tokyo Tech is working hard
to develop
university satellites, the 1st of which has
already been launched in 2003 June
CUTE-1.7
will measure low-E (E>3 keV)
e-/p distributions in SAA and aurora band
Hu-ring
can detect GRBs in 0.5-500 keV
and localize the position with 5’ accuracy
5: application to “NeXT” (JAPAN: 2010-)
×
g-ray
APD
SGD
BGO
Shield
HXI
SXI
Transparent
X-ray CCD
X-ray
Hard
X-ray
CdTe Pixel
Si Strip
APD
CsI
+APD
Electronics
modulation
collimator
APD is very compact, that
allows much more
design flexibility
than traditional PMTs
We are testing APDs as a read-out of BGO
anti-shield counter for both HXI and SGD.
BGO
plate
APD
(1x1 cm)
Light guide
30cm
5cm
Eth ~ 60 keV
In fact, large BGO plate was
successfully read-out by 1x1 cm
APD
(20.9% @662keV, Eth = 60 keV)
662 keV
(20.9% FWHM)
6: 2-dim APDs for imaging
purposes
We have developed 8x4 APD arrays (2x2 mm2 pixel each)
and read-out electronics (discrete/VA32TA)
for imaging purpose.
We will test the “polarization APD camera” by
using the
synchrotron radiation (~ 70 keV) at KEK Japan,
in May 2004.
Dark current, capacitance,
gain characteristics are very uniform
for all 32 pixels (see above for the response of 5.9 keV
X-rays)
We use APDs for the first time as a rad detector in space!
