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Kaori Hattori1,2
Chihiro Ida1,2, Kazuki Ito2, Kotaro Fujii3, Hidetoshi Kubo1,2,
Kentaro Miuchi1,2, Masaki Takata2,4,5, Toru Tanimori1,2, Hidehiro
Uekusa3
1Department of Physics, Kyoto University, Japan2 Structural
Materials Science Laboratory, RIKEN Harima Institute/SPring-8
Center, Japan3 Department of Chemistry and Materials Sicence, Tokyo
Institute of Technology, Japan4 SPring-8/JASRI, Japan5 Department
of Advanced Materials Sciences, Graduate School of Frontier
Sciences, The University of Tokyo*2008/8/30
IUCr 2008 Osaka, Japan
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OUTLINEDevelopment of detectors for structural
determinationRequirements for photon counting detectorsNovel photon
counting detector, mico-pixel chamber (m-PIC)Time resolved
experimentsSmall angle X-ray scattering (SAXS)
experimentsSummaryIUCr 2008 Osaka, Japan*2008/8/30
IUCr 2008 Osaka, Japan
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IUCr 2008 Osaka, Japan*To provide powerful methods for
structural determination High speed Structural analysis of
biological macromolecules (protein materials radiation within a
couple of minutes High precision wide dynamic range of
>107realize high precision measurementsStructural determination
of materials with light elements Time resolved active dynamics
photon-induced phase transitionrecord continuum transition with a
time resolution of sec to sub-msec repeated measurements will
provide better time resolution
To satisfy these conditionsPhoton counting detectors with good
position resolutions are suitable2008/8/30
IUCr 2008 Osaka, Japan
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IUCr 2008 Osaka, Japan*1. Position resolution better than 100
m2. Counting rates > 107mm-2, >1000 MWPC (irradiated
locally)3. Large active area of > 150150 mm24. No dead region
(ex. junctions)5. Efficiency difference < 1 %6. Image distortion
< 1 %7. Operation at room temperature, low power consumption8.
Easy maintenance9. Low costs
A photon counting area detector based on a Micro Pixel Chamber
(m-PIC)has realized 4, 6, 7, 8, and 9.1, 2, and 5 are in
progress.3. A n active area of a m-PIC currently in use is 100100
mm2 A m-PIC with an active area of 300 300 mm2 has proved stable
runs. Verification experiments at a synchrotron radiation facility
are being planned.Readouts without intervalsCRP (continuous
rotation photograph) methodHigh gainsensitivity to low energy
X-rays of about 1 keVAnomalous X-ray scattering of sulfur
(2.3keV2008/8/30
IUCr 2008 Osaka, Japan
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IUCr 2008 Osaka, Japan*100 mm GEMgas electron
multiplier)140um70umMechanism for photon detectionPhotoelectric
effect in a gasEmitted electron runs until it loses a kinetic
energyIonizes atomsElectron clouds are amplified by a GEM(gas
electron multiplier, F. Sauli, 1997) , and -PICPixel pitch400 mGas
gainm-PIC : 3104 GEM: 3
IUCr 2008 Osaka, Japan
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IUCr 2008 Osaka, Japan*m-PIC is kept in the sealed vesselThe
m-PIC is contained in a sealed vessel with a polyimide entrance
window of 0.1-mm thickness.The vessel is filled with Xe-C2H6(70:30)
gas.Stable operation without freshgas supply for > 1 monthSealed
vesselAnode 256ch + cathode 256chSignals from the -PIC are sent via
the printed circuit boards100 mm2008/8/30
IUCr 2008 Osaka, Japan
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*IUCr 2008 Osaka, JapanThe output charges of the 256+256
channels are parallel pre-amplified, shaped, and discriminated by
the ASD chips completely digitizedDigital signals are sent to the
position encoding module with an internalclock of 100 MHz, allowing
the recording of position (X or Y) and the timing Tin the memory
module2008/8/30
IUCr 2008 Osaka, Japan
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SimpleLow costEasy adjustments for detectors with large active
areaFast readout Characteristic less depends on counting ratesGood
counting rate capabilitiesm-PIC > 1 MHz charge division < 1
MHz delay line
IUCr 2008 Osaka, Japan*2008/8/30
IUCr 2008 Osaka, Japan
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*the best fit of exponential functionx1.038Error0.7%Irradiated
scattering froma piece of glassy carbon 0.9 IUCr 2008 Osaka,
Japangood linear correlation from 20 cps to 5 Mcps
Dynamic range of > 105No saturation
counting rates are limited by a high voltage module
2008/8/30
IUCr 2008 Osaka, Japan
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*400m10cm2-dimensional imaging gaseous detectorpitch 400m,size
100 mm100 mm, 300 mm300 mmposition resolution ~ 120mX-ray image of
test chart and the projected image along 0.5 mm slitsProjected
image of the test chart edge and the best fit of the error
functionTakeda et al., IEEE Transactions on nuclear science, Vol.
51, No.5, (2004) Theoretical limitKnife edge test2008/8/30IUCr 2008
Osaka, Japan
IUCr 2008 Osaka, Japan
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2008/8/30IUCr 2008 Osaka, Japan*CRP (continuous rotation
photograph) methodMovie of diffraction spots from rotating crystals
a crystal rotated by a goniometer timings of incident photons
converted to rotation angles of diffraction spots
Reducing the measurement timeStrong background reduction using a
new parameter, rotation angle
IUCr 2008 Osaka, Japan
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integrated diffraction spots
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IUCr 2008 Osaka, Japan*Movie varying 2q continuously Time
resolution of ~ 100 ns for each X-ray Much Information -> quick
online analysisTimeMSGC(Micro Strip Gas Chamber)Reciprocal
lattice2008/8/30
Crystal Ref. #R-factor (I > 2s ) time (sec.)
C4H9NO61,4067.9%2.1C20H37CoN6O44,3619.8% 300C25H26O44,5658.4%
80
IUCr 2008 Osaka, Japan
- Applying the noise reduction using 2q information rotation
speed : 4.89 sec/cycle mesurement time : 3716 sec counting rate :
1.05104 cpsTakeda et al.J. Synchrotron Rad. (2005)12, 820-8253716s
2q
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IUCr 2008 Osaka, Japan*BL14A17.5keVPICcrystal 2008/8/30
IUCr 2008 Osaka, Japan
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IUCr 2008 Osaka, JapanhydratedehydrateKEK Photon Factory
0.7Dehydration reaction of a pyromellitic acid hydrate occurs while
heat is applying (140)65 secChange in a diffraction pattern in 7
sec2008/8/30*
IUCr 2008 Osaka, Japan
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*0 sec1.95 sec3.90 sec6.50 secThe intensity I(2, t) is expressed
as I = xId (2)+ (1-x)Ih (2),where Id (2), Ih (2) is the intensity
of the dehydrate, the hydrate, respectively, including a
background4.3104 events / 0.65 secTime resolution will be expected
to about 4 msec with a count rate of 10MHz
IUCr 2008 Osaka, Japan
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IUCr 2008 Osaka, Japan*Camera length
0.63.5mbeamtarget2008/8/30
IUCr 2008 Osaka, Japan
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*Diffraction patterns of collagen with a -PIC X-ray imaging
system with an accumulation of 106 events, 105 events, and 104
events, respectively.Signal-to-noise ratio in the background of the
diffraction pattern was improved0.9 , 1.2 105 cps2008/8/301122
IUCr 2008 Osaka, Japan
- solution scattering from polystyrene latex(110 nm, 5 mg / ml),
1.5 IUCr 2008 Osaka, JapanNo spatial distortion was observed100
mm2008/8/30*irradiating a grid mask with scattering from a piece of
glassy carbon, 1.5 The peaks observed at the holes on the mask
moved < 10 mm when the beam intensity was varied from 8 to 200
kcpsHoles were perpendicularly arrangedThe deviation from the
perpendicular was
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IUCr 2008 Osaka, Japan*q-4Polystyrene latex0.04 weight %solid
spheres of 110-nmdiameter1.5 exposure time : 154 sec
Incident photon flux1.5 1011 photons / s
dynamic range Six orders of magnitudeCCD: 104Imaging Plate:
105-6106Close to edge of the detectorLow detection
efficiency2008/8/30
IUCr 2008 Osaka, Japan
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*IUCr 2008 Osaka, JapanApo-Ferritin1.5 exposure time : 436
sec
Solution (m -PIC)Water (m -PIC)Solution water (m-PIC)R-AXIS
(IP)
Incident photon flux1.5 1011 photons / s
Deviation from IP was seen in high-q region.Signal to noise
ratio stronglyeffects on low-countingrates region.Further studies
are necessary.2008/8/30
IUCr 2008 Osaka, Japan
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2008/8/30*Achieved by Gamma-ray camera based on a -PIC
currentgoalpitch400 m200 mNumber of electrodes256 2561500
1500Active area100 100 mm2300300 mm2Gas gain5103 104 >
104Dynamic Range> 106107Intensity Range(Global)<
5MHz10MHzEfficiency uniformityseveral %< 1%distortionNoNo
IUCr 2008 Osaka, Japan
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good linear correlation > 105 (20 cps 5 Mcps)Position
resolution of 120 umCRP method : Rint (internal agreement
factor)3.7% Time resolved measurementsImage without
distortionDynamic Range of > 106
2008/8/30IUCr 2008 Osaka, Japan*
IUCr 2008 Osaka, Japan
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IUCr 2008 Osaka, Japan*A photon anode : a few signals for 100 ns
cathode : a few signals for 100 ns
coincidence
To avoid accidental coincidence Further improvements are
necessaryanode20 ns20 nscathodeChoose between two possibilities:One
is correctThe other causes accidental coincidence
Cut events when another event comeswithin approximately 20 ns
2008/8/30
IUCr 2008 Osaka, Japan
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Small-angle neutron scattering at JRR-3, Japan in
SeptemberSolution scattering experimentsat Spring-8, Japan in
October
Increase detection efficiencydyamic rangeConfirm consistency
underhigh and low-count rate environmentsLarge m-PIC with an active
areaof 300300 mm2 in developmentIUCr 2008 Osaka,
Japan*2008/8/30
IUCr 2008 Osaka, Japan
*First, Im going to refer structural determination and what are
necessary for improving it.Next, Im going to talk about
requirements for photon counting detectors.****The micro-pixel
chamber, we call it u-PIC, is being developed at Kyoto
University.This is a schematic of our detector. The detector is
contained in a sealed vessel, as shown in this photo,and filled
with a xenon gas. The detection area is here. When a photoelectric
effect occurs here,emitted electron runs unitil it loses a kinetic
energy. During this process, atoms in the gas are ionized.Electron
clouds move toward a gas electron multiplier placed above the
u-PIC.And then they amplified by the GEM and the u-PIC.
*The detectors data-acquisition system consists of
amplifier-shaper-discriminator (ASD) chips (Orito et al., 2004), a
position encoding module (Kubo et al., 2005), and a memory module
on the VME bus. A block diagram of the data acquisition system is
shown in Fig. 3. The output charges of the 256+256 channels are
parallel pre-amplified, shaped, and discriminated by the ASD chips
whose integration time constant is 80 ns. The time constant of
signals integrated by the ASD chips was determined by the
integration time of charges generated in the m-PIC. A reference
threshold voltage was commonly supplied to all the ASD chips. All
discriminated digital signals are sent to the position encoding
module consisting of Field Programmable Gate Arrays (FPGA) with an
internal clock of 100MHz, allowing the recording of the anode and
cathode coincident position= (X, Y) and the timing (t) in the
memory module. Thus, the position encoding is completely executed
by digital processing. ***Obtained by knife edge test*Time resolved
X-ray crystal structure analysis has been succeeded using other gas
detector, a micro strip gas chamber.**The CRP method provides a new
parameter, a rotation angle, so we can display diffraction spots in
a three-dimensional space. As shown in these figures, it gets
easier to apply good noise reduction. The diffraction spots
cluster. So, events outside clusters should be noises. The change
in the diffraction pattern is clearly recognized.*You can see the
diffraction pattern changes as heat is applying.The weight fraction
of hydrate decreased from 1 to 0 within 7 sec.We records the weight
fraction every 0.65 sec using 4.3 times 10 to the forth events.The
X-ray intensity was low, so the time resolution was not good, but
when a counting rate is 10 mega hertz,the time resolution would be
deduced 4 mili seconds from this experiment.*