DETECTOR TECHNOLOGY PROJECTINTERNATIONAL REVIEWCOMMITTEE 2013
December 10-11, 2013

SOI, MPGD, SCD, LiqTPC, FPIX, ASIC, CO2

KEK
Detector Technology Project

SOI PROJECT
v.4 Dec. 6, 2013, Yasuo ARAI (KEK)(v.4b Jan. 30, 2014 minor correction)

Contents:
1. Introduction ..................................................................................................................... 3
2. SOI Pixel Process ........................................................................................................... 4
2.1 Wafer Process ........................................................................................................................................... 4
2.2 Back Gate Effect & BPW ......................................................................................................................... 5
2.3 Sensor Layers ........................................................................................................................................... 6
2.4 High Resistive Wafer ............................................................................................................................... 7
2.5 Leakage current ....................................................................................................................................... 9
2.6 Multi

Project Wafer Run ..................................................................................................................... 10

2.7 Stitching ................................................................................................................................................. 11

3. Detector Developments ................................................................................................ 12
3.1 SEABAS Readout Board ........................................................................................................................ 12
3.2 Integration Type Pixel Detector (INTPIX) ........................................................................................... 13
3.3 X-ray Detector for Astrophysics (XRPIX) ............................................................................................. 15
3.4 XFEL Detector (SOPHIAS) ................................................................................................................... 17
3.5 Vertex Detector (PIXOR) ....................................................................................................................... 18
3.6 Low Temperature Applications ............................................................................................................. 19
3.7 Other Detector R&Ds............................................................................................................................. 21

4. Advanced R&Ds ............................................................................................................ 23
4.1 Double SOI ............................................................................................................................................. 23
4.2 3D Vertical Integration.......................................................................................................................... 26

5. Data Base ..................................................................................................................... 29
5.1 Development History ............................................................................................................................. 29
5.2 Collaboration Members ......................................................................................................................... 29
5.3 Master Thesis ......................................................................................................................................... 32
5.4 Publications ............................................................................................................................................ 33
5.5 External Fundings ................................................................................................................................. 37
5.6 Patents .................................................................................................................................................... 37

6. References .................................................................................................................... 372

"'%#('#"

The Silicon-On-Insulator (SOI) pixel R&D [i] is targeting to develop monolithic pixel
detectors for future high-energy physics experiments, X-ray experiments, and otherapplications. It integrates both radiation sensors and LSI circuits in one chip, and achieve
high-resolution and intelligent detectors.
Fig. 1 shows the schematic view of the SOI pixel detector (SOIPIX). The SOI wafer iscomposed of a thick, high-resistivity substrate (sensor part) and a thin low-resistivity Si layer(CMOS circuitry) sandwiching a buried oxide (BOX) layer. After removing the top Si and the
BOX layer in the region of the sensing node contacts, p or n dopant is implanted to thesubstrate. Then contact vias and metal connections from the p-n junction to the transistors
are created. The main advantages of the SOI detectors are;•

There is no mechanical bump bonding, so obstacles, which will cause multiple
scattering, are eliminated and smaller pixel size is possible.

•

Parasitic capacitances of sensing nodes are very small (~10fF), so large conversion
gain and low noise operation are possible.

•

Full CMOS circuitry can be implemented in the pixel.

•

The cross section of single event effects caused by radiation is very small. A latch-up
mechanism, which destroys conventional bulk CMOS LSI, is absent.

•

Unlike conventional CMOS process, there is no leakage path to bulk. Thus SOI
transistors are shown to work over a very large temperature range from 4K to 600K.

•

The technology is based on industry standards, and one of most promisingtechnology for future LSIs. Thus further progress and lower cost are foreseeable.

•

Emerging vertical (3D) integration techniques are a natural extension of the SOI
technology, so a much higher integration density is possible.

We have started this R&D in 2005 by collaborating with Lapis Semiconductor Co. Ltd (see
5.1 Development History). Our process is developed based on their 0.2 µm CMOS
fully-depleted (FD-) SOI process [ii].

3Fig. 1 Schematic view of the SOI Pixel Detector.

&#$+ $%#&& * % $ %#&& Main specifications of the process are summarized in Table 1. We have been trying
several kinds of high-resistivity wafers (CZ and FZ) for both n- and p-type wafers (see 2.4
High Resistive Wafer). To reduce development cost, we called academic sectors to join our
MPW runs (see 2.6 Multi Project Wafer Run). The process has 5 layers of metal and canbe implement MIM capacitor located on 3rd metal (Fig. 2) [iii].
Table 1. SOI pixel process specifications.
Process

0.2µm Low-Leakage Fully-Depleted SOI CMOS,
1 Poly, 5 Metal layers, MIM capacitor (1.5 fF/um2), DMOS option. Core (I/O)
Voltage = 1.8 (3.3) V

SOI wafer

Diameter: 200 mm!,Top Si: Cz, ~18 "-cm, p-type, ~40 nm thickBuried Oxide: 200 nm thickHandle wafer: 720 µm thick. Cz(n) ~ 700 "-cm,
FZ(n) ~ 7k"-cm, FZ(p) ~ 25 k"-cm, etc.
Thinned to 100 ~ 500 µm by mechanical grind, and chemical etching. Thenadequate impurity is implant, laser Annealed, and Al is plated (200 nm).

BacksideTransistors
Optional
process

Normal and low threshold transistors are available for both core and IO
transistors.
Three types of structures (body-floating, source-tie and body-tie) are available.
Buried p-well formation
Vertical integration with µ-bumps.

4Fig. 2. Upper structure of the SOI process.

    '  '   $*One of the major difficulties to build a radiation sensor in SOI wafer is the back gate effect.
Since the sensor and the transistors are located very near (~200 nm), transistors become
ON when high voltage is applied to the sensor (Fig. 4-a). To shield the electric field of thetransistors from the sensor voltage, we developed Buried Well (BW) process. We implantp(n)-type dopant without removing the top Si layer to create a buried p(n)-well region(BPW(BNW)) under the BOX. As shown in Fig. 4, leakage current of transistors becomesvery high at the back side voltage of above 10V if there is no BPW layer. However, thetransistor characteristic does not change at 100V by introducing the BPW layer. (Actually
there is no back gate effect seen even more than 200V).

Fig. 3. Cross sectional view of a typical SOI pixel detector.
5Fig. 4. NMOS transistor Ids-Vds curve and back side voltage. (a) Without BPW layer, (b) with
BPW layer connected to ground. By introducing the BPW layer, the back gate effect is fully
suppressed.

  & "&#% ,%& After introducing the BPW/BNW layers successfully, several structures that require
additional layers were proposed and introduced. Fig. 5 shows present possible layers underthe BOX. PS and NS layers are high-density implant region to create p+ and n+ region andcontact to metal layer. These implant will be done after removing top Si and SiO2 layers.
BP3 is same mask layer used in the BPW, and is used when deeper implant is required.
BP2 is deepest buried layer to create nested structure with the BNW.
We are using same layout both for n-type and p-type substrate. Therefore, when we
process p-type substrate p-implant and n-implant are reversed. Thus, in p-type substrate,
BPW mask is used for buried n-well, and BNW mask is used for buried p-well and so on.
As for the backside of the wafer, following processes are done normally.
i)Mechanical grind to desired thickness,ii)

Wet etching by 40um,

iii)

Implant of n (p) dopant to n(p)-substrate (depth ~ 0.5um),

iv)

Aluminum plating (~200 nm).

6

Fig. 5. Structure of the sensor part for n-substrate and p-substrate. Capital letters are layer
name and inside of parenthis shows actual doping.

    % &&') * % 

We have been mainly using high resistive SOI wafer from standard products of SOITEC
Co. The handle wafer is made in Czochralski (Cz) method (called HR1 wafer), which isn-type and has about 700 Ohm•cm resistivity. However, it is desirable to get much higher
resistivity to create thicker depletion depth with lower voltage. We asked SOITEC to makespecial SOI wafer by bonding with Floating Zone (FZ) wafer. That FZ wafers was supplied
from us since it is not easy to get 8" FZ wafer.
To do CMOS process on FZ wafer is not easy task since CMOS high temperatureprocess will cause slips in the wafer (Fig. 6 center). After careful tuning of the hightemperature process, we succeeded to process FZ-SOI wafer without major slips (Fig. 6
right).
Fig. 7 shows leakage current vs. depletion depth for different wafers. FZ(n) and FZ(p)wafers of 500um thick become full depletion with 112V and 55V respectively, while Cz(n)wafer needs 237V to deplete 260um thick wafer.

Fig. 6. X-ray inspections of FZ-SOI wafers and slips.
7

Fig. 7. Leakage current and depletion width of INTPIX3e chip fordifferent kinds of wafers. Backside of the Cz(n) wafer is mechanicalgrind only, while the FZ(n) and FZ(p) wafers are chemical etching is
also done after the mechanical grind.

Fig. 8. 1/C2 plot of the INTPIX4 detector measured at 1kHz.
Calculated resistivity from the corner voltage is 6.0 kOhm•cm and 1.1
kOhm•cm for FZ(n) and Cz(n) wafers respectively.
8  (%%"' 

While leakage current of the sensor is not so important for short integration time
applications, it is important for long integration time applications such as astronomical X-ray
observation and measurements that require good energy resolution.
Table 2 shows leakage current of a few detectors. CZ(n)(=HR1) wafer shows relatively
large leakage current (> 100nA/cm2@Room Temp.), while FZ(n) wafer shows better leakage
current (10nA/cm2@20ºC). Fig. 9 shows temperature dependence of the XRPIX1 leakage
current. By lowering temperature, leakage current will decrease but become constant below-20 ºC. We have not yet identified the source of the constant leak curent.
Table 2. Summary of leakage current @Vdet=10V.
Chip/TEG

Wafer

Temp.

Leakage current

XRPIX1XRPIX1XRPIX1XRPIX1
MAMBO IV (nested well)
INTPIX/CNTPIX

Cz(n)
Cz(n)
FZ(n)
FZ(n)
FZ(n)
Cz(n)

25 ºC
-50 ºC
20 ºC-20 ºCRoom T
Room T

440 nA/cm2
0.3 nA/cm2
10 nA/cm2
0.1 nA/cm2<100 nA/cm2
100~300 nA/cm2

Fig. 9. Dark Current of the XRPIX1 FZ-SOI. Pixel size is 30.6 um square.
Target spec is 2pA/cm2.

9

Fig. 10 shows Arrhenius plot of the XRPIX2b-Cz(n). Until full depletion occurs around
250V, the activation energy is about 0.55eV. This implies main source of the current comesfrom generation current in the depletion region. When full depletion achieved above 300V,
activation energy decreases below 0.35eV. This implies back side surface is the source of
the additional leakage current.

Fig. 10. Arrhenius plot of the XRPIX2b-Cz(n) detector.

  ! ( '  $ %#' * % % (" The cost of semiconductor process is not cheap. Major part of the cost is mask set. To
reduce development cost and have multiple chances for developments, we decided tooperate this SOI pixel process as Multi Project Wafer (MPW) runs. In past a few years, wehave been doing the MPW runs twice per year except year 2011 when large earthquake wasoccurred and Lapis semiconductor fab was damaged.
In addition to many Japanese institutes, we have been collaborating with
US/Europe/Asian researchers through this MPW runs. Our present collaborator/user are
listed in section 5.2 "Collaboration Member"
In 2011, we changed the mask size from 20.6mm x 20.6mm to 24.6mm x 30.8mm, so that
we can accept more designs and build larger detector Fig. 11.

10

Fig. 11.. Examples of Mask layouts. (Left) FY2010 : 20.6mm x 20.6mm.

  & ''" 

Large area detectors are often required in some experiments, but the mask size is limited
to 24.6mm x 30.8mm in size. Therefore, we have developed stitching technique to makelarge format detector by using only one mask set. Fig. 12 shows the stitching method andphotographs of the processed wafer.
The development is mainly driven by Riken group for the SOPHIAS detector. Since thiswas our first trial, we took buffer region size of 10um and connect only minimum number oflayers (PS, NS and metal 1). However, Lapis is confident to make buffer region shorter andconnects all metals.

11

Fig. 12. Stitching exposure for the SOPHIAS detector. Both edge structure and pixel structure weredrawn in a mask. Part of the mask is blocked during exposure. In this detector (SOPHIAS), pixel
layout was repeated 3 times and edge structures are exposed at both ends.

''#%) #$!"'&

There are many activities of detector developments using the SOI pixel process. In thissection, we flash major activities of the developments.
 &&  % #('  #% 

To test manufactured chip quickly, we have developed SEABAS (SOI EvAluation BoArd
with Sitcp) read out board. The board contains two FPGAs one for controlling the SOI pixel
and the other is for transferring the data through Ethernet (called SiTCP).
Fig. 13 and Fig. 14 show block diagram and photograph of the SEABAS2 (2nd generation
board) respectively. By using the SEABAS2 board, we could take ~70 frame/sec withINTPIX4 detector (425k pixels).

12Fig. 13. Block diagram of the SEABAS2..

Fig. 14, Photograph of the SEABAS2 board and the INTPIX4 sub-board.

  "'%'#" ' ,$ $ +   ''#% "'$+

Main SOI detectors developed so far are integration-type pixel detectors. The basic
schematic of the sensor and a layout are shown in Fig. 15. The circuit is similar to that of the
CMOS optical imager. Smallest size of the pixel we have developed is 8 µm square. Many of
the integration-type pixels have correlated double sampling (CDS) circuit in each pixel or incolumn circuit. Largest chip (INTPIX5/6) so far tested has 896 x 1408 (~1.3 M) pixels, andnew chip (INTPIX7) under process has 1408 x 1408 (~2M) pixels. Specifications of major
integration-type detector are summarized in Table 3.
An example of X-ray image taken by the INTPIX4 detector is shown in Fig. 16.

13

Fig. 15. (Left) A typical circuit schematic of the integration-type pixel with CDS function. (Right) Layoutof INTPIX7 pixel. The size of the pixel is 12um x 12um.

Table 3. Specification of major integration-type pixel detectors.

Pixel Size [um]Chip Size [mm]
BPW width [um]CDSStore Switch
Wafer
Gain
Max. Charge
No. of Pixels
No. of Output
Rolling Shutter

DIPIX1/2

FPIX1

INTPIX4

INTPIX5/6

14 x 145x5
10Pixel CDS
O

8x8
6x6
6
-

17 x 1710.2 x 15.4
12
Pixel CDSOn or pn and pn

12 x 1212.2 x 18.4
9
Column CDS
O
n and p (INT5)n or p (INT6N or P)
2 gain(~16 or 2.5 uV/e-)~70 or 460 ke896 x 1408(~1,260 kpix

Fix(9.3 uV/e-)~110 ke256 x 128 x 2(~65 kpix)

1
-

Fix
Fix
(~28 uV/e-)(12.6 uV/e-)~40 ke80 ke512 x 512
512 x 832(~260 kpix ~430 kpix

1 or 9O

1 or 13-

1 or 11O

INTPIX7(under process)12 x 1218.4 x 18.4
9
Pixel CDSO
p (Double SOI)
Fix
1408 x 1408(~1,982 kpix

1 or 11O

14

Fig. 16 An example of X-ray image (small fish) taken by the integration-type SOI sensor.

   + %,  ''#%#%  &'%#$,&& +%$+

XRPIX detector [iv] has been developed for X-ray astronomical satellite by Kyoto Univ.
and KEK/SOKENDAI member. Basic structure of the detector is same as that of theintegration type detector, but it also has trigger generation function. By combining the trigger
function and active shield system, background event caused by charged particles can beremoved (Fig. 17).
In addition to source-follower type pixel used in the INTPIX, we have also developed
Charge Sensitive Amplifier (CSA) type pixel recently. Fig. 17 shows energy spectrum of 55Fe
X-rays taken by the XRPIX CSA pixel. CSA type pixel shows much better resolution
compared to source follower type, and achieved noise level of 33 e- while source follower
type has 76 e- noise level.

15

Fig. 17 Concept of an active shield system with the XRPIX. Non-X-ray background can berejected by anti-coincidence with the active shield (scintillation counters).

Fig. 18 Block diagram of the XRPIX detector.

16

Fig. 19. Energy spectrum of 55Fe taken with the XRPIX detectors. CSA type pixel showed better
resolution.

   +   ''#% &#$&

A large dynamic range X-ray image Sensor has been developed for X-ray Free-electron
Laser Facility, SACLA. The detector is named SOPHIAS (Silicon-On-Insulator PHoton
Imaging Array Sensor) and developed by Riken group [v]. The sensor consists of 1.9 M
pixels with 30 um pixel square shape. The single layer sensor give 40 % quantum efficiency
at 20 keV X-ray photons with 500um thick handle wafer.
Each pixel has high and low gain channels to achieve large dynamic range. The different
gain is achieved by different value of the input capacitance and different number of sensor
nodes (Fig. 20). To fabricate larger detector than mask size, stitching technique is developed
and used (see 2.7 Stiching).

17

Fig. 20. Outlook of the SOPHIAS detector and schematics of the pixel.

   ) %'+  ''#% $+#%

As an R&D for future vertex detector for Belle II experiment, a new detector PIXOR (PIXelOR) is being developed by Tohoku Univ. group [vi]. An analog signal from each pixelated
sensor is divided into two-dimensional directions, and 2N signal channels from a small
N-by-N pixel matrix are ORed as N column and N row channels (Fig. 21). Then the signals
are processed by a readout circuit in each small matrix and wait for a trigger (Fig. 22).
This PIXOR scheme reduces the number of readout channels and avoids a deteriorationof intrinsic position resolution due to large circuit area that was a common issue formonolithic detectors. This feature allows high resolution, low occupancy and on-sensor
signal processing at the same time.

18

Fig. 21. Conceptual view of PIXOR (4x4 Super Pixel case). A charged particle penetrates the green
pixel. The signal is divided into X(blue)/Y(red) directions. In this figure, readout circuit is notshown.

Fig. 22 Schematic of the single channel PIXOR1 circuit.

   #* ' !$%'(%  $$ '#"& People in JAXA/ISAS have interest in using SOI devices in cryogenic temperature. Theydeveloped CMOS amplifiers and switches by using the SOI process, and confirmed to workwithout problem in low temperature where bulk CMOS devices cannot work. Typicalperformance of the amplifier is shown in Table 4.

19

Table 4. Performance of FD-SOI CMOS amplifier at 4.2K.

After the success of the cryogenic operation, we started a project to build
Superconducting Tunnel Junction (STJ) devices on processed SOI wafer with Univ. of
Tsukuba group. When we want to arrange the STJ devices in array, extraction of STJ
signals to room temperature is always annoying issue. If we succeed to build the STJ on
processed SOI wafer and make good connections between them, number of the connection
can be greatly reduced and S/N can be improved.
We have tested characteristics of SOI transistors at below 1K (Fig. 23). Both NMOS andPMOS show good performance. Then we build Nb/Al STJ device on top of the SOI wafer.
The STJ devices successfully build and output signal is observed by illuminating laser light(465 nm) to the device (Fig. 24).

Fig. 23. Ids-Vgs characteristics of NMOS and PMOS transistors at 960mK and 750mK respectively.

20

Fig. 24. (Left) Test structure of an element. (Right) Signal from the Nb/Al-STJ
built on the SOI wafer.

   # '%  ''#% % & 

There are many other detectors R&Ds which are going on by using our MPW run.
Counting-type pixel (CNTPIX)
One of most important R&D for next step is development of counting type detectors.
Schematic of the counting type pixel and its pixel layout are shown in Fig. 25. We alreadyhave test chips that show proper responses, but we also observe crosstalk between sensor
and the circuits. Thus the development is postponed until double SOI technology is available(4.1 Double SOI).

Fig. 25. (Left) Schematic of the counting type pixel (CNTPIX). (Right) layout of the counting type pixelof 64um x 64um size.
21

Detector for Imaging Mass Spectrometer (MALPIX)
Multi-Turn Time of Flight Mass Spectrometer (MULTUM) is being developed at Osaka
Univ. as a compact and high performance mass spectrometer for next generation. It requires
two-dimensional detector that can measure ion arrival timing in 1 ns resolution. Although it
does not use sensor part of the SOIPIX, our pixel circuit can be utilized for this application.
Then we started collaboration with Osaka group and developing a pixel detector called
MALPIX. Ions from the spectrometer are converted to electrons by using Micro-Channel
Plate (MCP), and a prototype detector was successfully tested.

Fig. 26. (Top) Overview of the MULTUM mass spectrometer. (Bottom) Schematics ofthe MALPIX.

LHD pixel
To investigate inside of nuclear fusion plasma, measurement of X-rays from the inside ofplasma gives valuable information. We have started collaboration with National Institute for22

Fusion Science (NIFS) for measurement of Large Helical Device (LHD). First test isscheduled on Dec. 2013.
TDI pixel
X-ray detectors are used widely in many kinds of inspection system. Especially to findsmall metallic debris of ~10um size within battery has crucial demand in future electricalvehicles and so on. To find such small debris from materials on high-speed belt conveyor,
SOIPIX is very suitable with its high resolution. However, to receive enough X-rays frommoving object, Time Delayed Integration (TDI) method is mandatory. Although it is easy to
implement the TDI in CCD device, it is difficult to do in CMOS device. We have invented a
new method to implement digital TDI in the SOIPIX.
RADPIX
After the accident of the Fukushima nuclear power plant, people become very sensitive toradiations. Although SOIPIX does not have high efficiency for a few hundreds keV gamma
rays, pixelated sensor has advantage to identify type of the radiation and detection of alphaand beta rays. Thus we are developing a pixel detector (RADPIX) for monitoring
environmental radiation. It includes leakage current compensation circuit for continuous
detection of radiation.
)"%&  #(  &#

While we solved the back gate problem by introducing BPW layer, there still remain two
issues to make the SOIPIX used widely.
• Crosstalk between sensor node and circuit,• Radiation tolerance of the detector.
The crosstalk generates unwanted signals and makes operation of the detector unstable.
While the SOI is immune to Single Event Effect (SEE), it is not so rad-hard to Total Ionization
Dose (TID) due to the BOX and surrounding oxide. Tolerable radiation level of present
SOIPIX devices is about 2 kGy, and many applications require more than 10 kGy (1 Mrad)
tolerance.
After all, to solve these issues, we need another conduction layer between sensor andcircuit. We asked SOITEC to make double SOI wafer which has two sets of thin Si and BOX
pair layers. General view of the double SOI pixel detector is shown in Fig. 27, and crosssection of processed double SOI wafer is shown in Fig. 28. In addition to above two issues,
the newly introduced middle Si layer (SOI2) shields back gate effect too (Fig. 29), so that we
can optimize the size of the BPW without considering the back gate effect.

23

Fig. 27. General view of the pixel detector using the double SOI wafer.

Fig. 28. Cross sectional view of the double SOI wafer. In addition to top SOI and substrate,
we introduced middle SOI layer. (Unfortunately, the contact to the middle Si is out of thephotograph.)

The first double SOI wafers were produced by SOITEC Co. with n-substrate, but second
DSOI wafers have been produced by Shin-Etsu Chemical Co. Ltd, Japan, with p-type
substrate.
When we irradiate gamma rays to the SOI, transistor threshold voltage will move tonegative direction (Fig. 29 left) due to hole trapping in the oxide. However, by applying
negative voltage to the middle Si, electric field generated by the hole is compensated andthe threshold voltage will return to almost original value (Fig. 30).

24

Fig. 29. Back gate effect suppression by the middle Si. (Left) Middle Si is floating. (Right) Middle Si
is connected to ground and the back gate effect is fully suppressed.

Fig. 30. Id-Vgs curve change with g-ray irradiation and middle Si voltage (VSOI2). (Top) NMOS,(Bottom) PMOS.

Fig. 31 plots optimum value of the SOI2 layer to return the threshold value to original value[vii]. The statistics of the data is not yet enough and there is large variation in the data of
NMOS core transistors. However we can see the optimum value for dose up to 20 kGy looks
same for all the transistors. On the other hand, at above 20 kGy, we see some rebound in25

NMOS transistors. Then we may need to separate the SOI2 layer between NMOS andPMOS for the application that requires more than 20 kGy radiation tolerance.

Fig. 31. Optimum SOI2 value to return threshold for various kinds of transistors. Both 'NMOS and
PMOS' and 'Core and IO' transistors are showing similar tendency.

   ) %'   "'%'#" Although the SOI detector is successfully being developed, future pixel detectors such as
used in the International Linear Collider (ILC) requires much more transistors to implement
memories and data processing logics than available today. Since the readout circuit needs
analog amplification circuits etc., it is not necessary good to go fine node process.
If we try to implement such memory and logics inside the pixel, the pixel size must be verylarge (> 60 x 60 um2), while the experiment requires smaller pixel size less than 20 x 20 um2.
To solve this, we have started R&D of 3D vertical integration by using µ-bump technology[viii] in collaboration with T-Micro Co.
Fig. 32 shows the process flow of the vertical stacking of circuit layers. Base SOI chips as
upper and lower tiers are fabricated in a SOI wafer. Minimum bump pad opening size is 3µm x 3 µm. After forming under bump metallization (UBM), Indium bumps are formed using26

evaporation and lift-off technique. The minimum bump size and pitch are 2.5-µm sq. and 5µm respectively.
Lower tier and upper tier are aligned using IR microscope. Initial alignment error before
welding bumps must be kept less than 1.0 µm in order to obtain stable electrical connection.
After fusing into one connection, the tiers are self-aligned to less than 0.6 µm. The gap
between tiers is about 1.5 µm. An array of Indium µ-bump junctions does not have enoughmechanical strength. So combining gap fill with adhesive is indispensable and injection
method is the key of this process.
Fig. 33 shows layout of alignment mark and photographs of the alignment marks at 4

corners after the bonding and the adhesive injection. The chips are aligned at better than 1
um accuracy. Since the space between tiers is not uniform due to unbalance distribution ofthe µ-bumps in the chip, adhesive injection caused voids at the points where rapid pressure
loss occurs. White island area seen in Fig. 33-bottom upper left photo is such a void. Numberof the voids is greatly reduced by controlling differential pressure assisted capillary action.
Although we are bonding chip to chip in this study, chip to wafer bonding techniques are also
being developed for mass production.

Fig. 32. Process flow for the stack process with micro bump technology.
27

Fig. 33. (Top) Alignment mark size, (Bottom) Alignment of upper and lower chips after stacking.

28'&  ) #$!"'  &'#%, 2005. 52005. 7

Propose SOI Pixel R&D to KEK Detector Technology ProjectStart Collaboration with OKI Electronics Co. Ltd.

2005.10
2006.122007.3First submission to Univ. of Tokyo (VDEC) 0.15µm SOI MPW run.
First MPW run of 0.15um SOI process operated by KEK.
First SOI Workshop @KEK

2007. 6
2007.10Process change to Miyagi 0.2um line due to discontinue of Hachioji 0.15 µm line.
First User Meeting @U. of Hawaii (IEEE NSS)

2008. 1
2008.32008.10First MPW run of 0.2µm SOI process.
SOI Workshop @KEK
OKI semiconductor division was spin-off to OKI semiconductor Co. Ltd, and enters
under Rohm Co. group.
Metal Pitch is shrunken from 0.88um to 0.58um.
Introduce Buried P-Well structure.
SOI W.S. @Kyoto Univ.
Collab. Mtg. @Fermilab
International Review @KEK
OKI Semi Miyagi Fab. was damaged by the large earthquake.
Name of OKI Semi was changed to Lapis Semiconductor Co. Ltd.
Mask size was increased from 20.6 mm square to 24.6 mm x 30.8 mm.
Collab. Mtg. @LBNL
First double SOI wafer was processed.
PIXEL2012 conference @Fukushima.
Mini Workshop @IHEP (China)
Collab. Mtg. @Krakow (AGH & IFJ)
10th 0.2um MPW run was submitted.

2009. 1
2009.2
2010.32011.2
2011.32011.92011.102012.32012.82012.92013.2
2013.52013.8##%'#" ! !%& [Japanese Members]
Name
Koichi NAGASE
Hirokazu Ikeda
Testuichi Kishishita
Daisuke Kobayashi
Takehiko WADA
Ryuichi Takashima
Shou Moritake
Shinya Nakashima
Hironori Matsumoto
Syukyo G. Ryu
Takeshi Tsuru
Takaaki Tanaka
Hideaki Matsumura

Affiliation
JAXA/ISAS
JAXA/ISAS
JAXA/ISAS
JAXA/ISAS
JAXA/ISAS
Kyoto Univ. of Education
Kyoto Univ. of Education
Kyoto Univ.
Nagoya Univ.
Kyoto Univ.
Kyoto Univ.
Kyoto Univ.
Kyoto Univ.
29

Jiro Ida
Kazuya Tauchi
Ryo Ichimiya
Susumu Terada
Takashi Kohriki
Tomohisa Uchida
Toru Tsuboyama
Toshinobu Miyoshi
Yasuo Arai
Yoichi Ikegami
Yoshinobu Unno
Yowichi Fujita
Yukiko Ikemoto
Shingo Mitsui
Motohiko Omodani
Takashi Kameshima
Hirofumi Tadokoro
Masashi Yanagihara
Morifumi Ohno
Yasushi Igarashi
Hidehiko Nakaya
Ayaki Takeda
Daisuke Nio
Kazunori Hanagaki
Minoru Hirose
Toshihiro Idehara
Kazuhiko Hara
Yuji Takeuchi
Shinhong Kim
Mari Asano
Naoshi Tobita
Tatsuya Maeda
Kouhei Tsuchida
Shunsuke Honda
Kouta Kasahara
Kouhei Shinsho
Yoshiyuki Onuki
Hideki Hamagaki
Yuuko Sekiguchi
Hitoshi Yamamoto
Akimasa Ishikawa
Yutaro Sato
Hironori Katsurayama
Shinoda Naoyuki
Yoshimasa Ono
Kouji Mori
Yuusuke Nishioka
Kazuo Kobayashi
Shun Ono
Takaki Hatsui
Tougo Kudo
Kameshima Takashi
Yoichi Kirihara

Kanazawa Institute of Technology
KEK, High Energy Accelerator Research Organization
KEK, High Energy Accelerator Research Organization
KEK, High Energy Accelerator Research Organization
KEK, High Energy Accelerator Research Organization
KEK, High Energy Accelerator Research Organization
KEK, High Energy Accelerator Research Organization
KEK, High Energy Accelerator Research Organization
KEK, High Energy Accelerator Research Organization
KEK, High Energy Accelerator Research Organization
KEK, High Energy Accelerator Research Organization
KEK, High Energy Accelerator Research Organization
KEK, High Energy Accelerator Research Organization
KEK, High Energy Accelerator Research Organization
JASRI, XFEL division
JASRI, XFEL division
National Institute of Advanced Industrial Science and Technology
National Institute of Advanced Industrial Science and Technology
National Institute of Advanced Industrial Science and Technology
National Institute of Advanced Industrial Science and Technology
National Astronomical Observatory of JapanThe Graduate University for Advanced StudiesSchool of High Energy
Accelerator
The Graduate University for Advanced StudiesSchool of High Energy
Accelerator Science
Department of Physics, Osaka Univ.
Department of Physics, Osaka Univ.
Department of Physics, Osaka Univ.
Univ. of Tsukuba, Faculty of Pure and Applied Sciences
Univ. of Tsukuba, Faculty of Pure and Applied Sciences
Univ. of Tsukuba, Faculty of Pure and Applied Sciences
Univ. of Tsukuba, Graduate School of Pure and Applied Sciences
Univ. of Tsukuba, Graduate School of Pure and Applied Sciences
Univ. of Tsukuba, Graduate School of Pure and Applied Sciences
Univ. of Tsukuba, Graduate School of Pure and Applied Sciences
Univ. of Tsukuba, Graduate School of Pure and Applied Sciences
Univ. of Tsukuba, Graduate School of Pure and Applied Sciences
Univ. of Tsukuba, Graduate School of Pure and Applied Sciences
Univ.of Tokyo
Univ.of Tokyo
Univ.of Tokyo
Tohoku Univ.
Tohoku Univ.
Tohoku Univ.
Tohoku Univ.
Tohoku Univ.
Tohoku Univ.
Miyazaki Univ.
Miyazaki Univ.
RIKEN, RIKEN SPring-8 Center
RIKEN, RIKEN SPring-8 Center
RIKEN, RIKEN SPring-8 Center
RIKEN, RIKEN SPring-8 Center
RIKEN, RIKEN SPring-8 Center
RIKEN, RIKEN SPring-8 Center30

Sadatsugu Muto
Shigeru Sudo
Naoki Tamura
Yasuhiko Ito
Hideya Nakanishi
Tsukada Kiwamu
Masayuki Ikebe
Shoji Kawahito
Keiichiro Kagawa
Keita Yasutomi
Takeo Watanabe
Nobukazu Teranishi

National Institute for Fusion Science
National Institute for Fusion Science
National Institute for Fusion Science
National Institute for Fusion Science
National Institute for Fusion Science
Nagoya Institute of Technology
Hokkaido Univ.
Shizuoka Univ.
Shizuoka Univ.
Shizuoka Univ.
Univ. of Hyogo
Univ. of Hyogo[Foreign Members]
Name
Chih Hsun Lin
Minglee Chu
Sebastian Glab
Wojciech Kucewicz
Marek Idzik
Mohammed Imran Ahmed
Piotr Kapusta
Farah Khalid
Grzegorz Deptuch
Marcel Trimpl
Raymond Yarema
Ronald Lipton
Ivan PericPeter Fischer
Lei FanLiu Gang
Xiaoshan JIANG
Yunpeng Lu
Zheng Wang
Yi LiuQi Zhang
Ning Wang
Tian Li
Hui Wang
Qi Zhang
Zhao Kai
Chinh Vu
Devis Contarato
Lindsay GlesenerPeter Denes

Affiliation
Academia Sinica, Taiwan
Academia Sinica, Taiwan
Department of Electronics AGH-University of Science and Technology(AGH-UST)
Department of Electronics AGH-University of Science and Technology(AGH-UST)
Krakow's University of Science and Technology (AGH-UST)
Institute of Nuclear Physics, Krakow
Institute of Nuclear Physics, Krakow
Fermilab
Fermilab
Fermilab
Fermilab
FermilabInstitut für Technische Informatik der Universität Heidelberg
Institut für Technische Informatik der Universität Heidelberg
Institute of High Energy Physics, Chinese Academy of Sciences
Institute of High Energy Physics, Chinese Academy of Sciences
Institute of High Energy Physics, Chinese Academy of Sciences
Institute of High Energy Physics, Chinese Academy of Sciences
Institute of High Energy Physics, Chinese Academy of Sciences
Institute of High Energy Physics, Chinese Academy of Sciences
Shanghai Advanced Research Institute, Chinese Academy of Sciences.
(SARI, CAS)
Shanghai Advanced Research Institute, Chinese Academy of Sciences.
(SARI, CAS)
Shanghai Advanced Research Institute, Chinese Academy of Sciences.
(SARI, CAS)
Shanghai Advanced Research Institute, Chinese Academy of Sciences.
(SARI, CAS)
Shanghai Advanced Research Institute, Chinese Academy of Sciences.
(SARI, CAS)The Institute of Microelectronics of the Chinese Academy of Sciences(IMECAS)
LBNL
LBNL
LBNL
LBNL

31

Craig S Tindall
Marco Battaglia
Eduardo Cortina
Elena Martin
Lawrence Soungyee
Paula liliana alvarez
rengifoGary Varner
Michael Cooney
Angel Dieguez
Dario BiselloDevis Pantano
Serena Mattiazzo
Piero Giubilato

LBNL
LBNL, UC Santa Cruz
Louvain-la-Neuve University
Universitat Autonoma de Barcelona
Louvain-la-Neuve University
Louvain-la-Neuve University
Univ. of Hawaii
Univ. of Hawaii
University of Barcelona
University of Padova & INFN Padova, Italy
University of Padova & INFN Padova, Italy
University of Padova & INFN Padova, Italy
University of Padova and INFN Padova, Italy, & LBNL,

USA[Cooperation Companies]
Name
Lapis Semiconductor Co. Ltd.
Lapis Semiconductor Miyagi Co. Ltd.
A-R-Tec Co.
Rigaku Co.
T-micro Co. Ltd.
REPIC Co. Ltd.
Digian Technology Inc.

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;2'?A7A.-H!-> ĸ ,A@->; &-@;A J©İ~q]e}^lUQXUĒÿðuxÎózqkUúýĮ÷KH²ğ
ÚHH';4;7A(:5B H!-> ĸ &EA7E; %EAJ&# Òđ\õLQêTMN[ÊÇ¯ĽĆÖå§UĮ÷MZVěĜĴKHE;@;(:5B H1. ĸ !5:;>A5>;?1J&# Òđ\õLQ­ $5D18 å§õĞWOginxUĮ÷H¢Vü­ $5D18å§UÐĊěKH#?-7-(:5B H1. ĸ ,A65&-13A?- J&# Òđ\õLQÁå§UĮ÷KH';7E;:?@ ;2'1/4 H1. ĸ 5!;/45FA75 J&585/;:#::?A8-@;> Òđ\õLQĞO¨ģ­g~evcjå§UĮ÷úýKH(:5B ;2'?A7A.-!->    $ ( '#"& [English]1 "Hard X-Ray SOI Sensor Prototype", E. Martin, G. Varner, M. Barbero, J. Kennedy, H. Tajima, Y. Arai,IEEE Ph. D. Research in Microelectronics and Electronics, 11 - 16 June 2006, Otranto (Lecce), Italy
2 "First Results of 0.15um CMOS SOI Pixel Detector", Y. Arai, M. Hazumi, Y. Ikegami, T. Kohriki, O. Tajima,
S. Terada, T. Tsuboyama, Y. Unno, H. Ushiroda, H. Ikeda, K. Hara, H. Ishino, T. Kawasaki, E. Martin, G.
Varner, H. Tajima, M. Ohno, K. Fukuda, H. Komatsubara, J. Ida, SNIC Symposium, Stanford, California,
3-6 April 2006, SLAC-PUB-12079, KEK preprint, 2006-34, SLAC Electronic Conference Proceedings
Archive(SLAC-R-842,
eConf:
C0604032)
PSN-0016.
http://www.slac.stanford.edu/econf/C0604032/papers/0016.PDF.
3 "Monolithic Pixel Detector in a 0.15mm FD-SOI Technology", Y. Arai,presented at the 6th Hiroshima
symposium of Development and Application of semiconductor tracking devices, Sep. 11-15, 2006,
Carmel, California, U.S.A.
4 "Development of a CMOS SOI Pixel Detector", Y. Arai, M. Hazumi, Y. Ikegami, T. Kohriki, O. Tajima, S.
Terada T. Tsuboyama, Y. Unno, Y. Ushiroda, H. Ikeda, K. Hara, H. Ishino, T. Kawasaki, H. Miyake, E.
Martin, G. Varner, H. Tajima M. Ohno, K. Fukuda, H. Komatsubara, J. Ida,Proceedings of 12th Workshop
on Electronics for LHC and Future Experiments (LECC 2006), 25-29 September 2006, Valencia SPAIN.
5 "Monolithic Pixel Detector in a 0.15um SOI Technology", Y. Arai, M. Hazumi, Y. Ikegami, T. Kohriki, O.
Tajima, S. Terada, T. Tsuboyama, Y. Unno, H. Ushiroda, H. Ikeda, K. Hara, H. Ishino, T. Kawasaki, E.
Martin, G. Varner, H. Tajima, M. Ohno, K. Fukuda, H. Komatsubara, J. Ida, H. Hayashi,, IEEE Nuclear Sci.
Symposium, San Diego, Oct. 29 - Nov. 4, 2006, Conference Record, Vol. 3, Oct. 2006 Page(s):1440 1444, Digital Object Identifier 0.1109/NSSMIC.2006.354171.
6 "Evaluation of OKI SOI Technology",Y. Ikegami, Y. Arai, K. Hara, M. Hazumi, H. Ikeda, Ishino, T. Kohriki,
H. Miyake, A. Mochizuki, S. Terada, T. Tsuboyama, Y. Unno,, presented at the 6th Hiroshima symposiumof Development and Application of semiconductor tracking devices, Sep. 11-15, 2006, Carmel, California,
U.S.A., Nuclear Instruments and Methods in Physics Research Section A, Volume 579, Issue 2, 1 Sept.
2007, Pages 706-711,
7 "Deep sub-micron FD-SOI for front-end application", Nuclear Instruments and Methods in Physics
Research Section A, Volume 579, Issue 2, 1 September 2007, Pages 701-705, H. Ikeda, Y. Arai, K. Hara,
H. Hayakawa, K. Hirose, Y. Ikegami, H. Ishino, Y. Kasaba, T. Kawasaki, T. Kohriki, et al., Proceedings ofthe 11th Symposium on Radiation Measurements and Applications (SORMA XI): Ann Arbor, USA, May
23_26, 2006, Nucl. Instr. and Meth. A, Vol. 579, Issue 2, 1 Sep. 2007, p.p. 701-705.
8 "Electronics and Sensor Study with the OKI SOI process", Y. Arai, , Topical Workshop on Electronics for
Particle Physics (TWEPP-07), 3-7 Sep. 2007, Prague, Czech Republic. CERN-2007-007, pp. 57-63.
9 "SOI Monolithic Pixel Detector R&D in a 0.15 mm SOI Technology", Y. Arai, Y. Ikegami, Y. Unno, T.
Tsuboyama, S. Terada, M. Hazumi, T. Kohriki, H. Ikeda, K. Hara, H. Ishino, H. Miyake, K. Hanagaki, G.
Varner, E. Martin, H. Tajima, Y. Hayashi, M. Ohno, K. Fukuda, H. Komatsubara, J. Ida., 16th
International Workshop on Vertex detectors, September 23-28, 2007, Lake Placid, NY, USA, Vertex 2007,
Poster Presentation.
10 "SOI Pixel Developments in a 0.15µm Technology”,, Y. Arai, Y. Ikegami, Y. Unno, T. Tsuboyama, S.
Terada, M. Hazumi, T. Kohriki, H. Ikeda, K. Hara, H. Miyake, H. Ishino, G. Varner, E. Martin, H. Tajima, M.
Ohno, K. Fukuda, H. Komatsubara, J. Ida, H. Hayashi, Y. Kawai, , 2007 IEEE Nuclear Science
Symposium Conference Record, N20-2, pp. 1040-1046.
11 "Total Dose Effects on 0.15µm FD-SOI CMOS Transistors”, , Y. Ikegami, Y. Arai, K. Hara, M. Hazumi, H.
33

Ikeda, H. Ishino, T. Kohriki, H. Miyake, A. Mochizuki, S. Terada, T.Tsuboyama and Y. Unno,, 2007 IEEE
Nuclear Science Symposium Conference Record, N44-6, pp. 2173-2177.
12 “A monolithic pixel sensor in fully depleted SOI technology”, , Marco Battaglia, Dario Bisello, Devis
Contarato, Peter Denes, Piero Giubilato, Lindsay Glesener, Chinh Vu. , Nuclear Instruments and Methods
in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
Volume 583, Issues 2-3, 21 December 2007, Pages 526-528.
13 "R&D of a pixel sensor based on 0.15 µm fully depleted SOI technology", Toru Tsuboyama, Yasuo Arai,
Koichi Fukuda, Kazuhiko Hara, Hirokazu Hayashi, Masashi Hazumi, Jiro Ida, Hirokazu Ikeda, Yoichi
Ikegami, Hirokazu Ishino, Takeo Kawasaki, Takashi Kohriki, Hirotaka Komatsubara, Elena Martin, Hideki
Miyake, Ai Mochizuki, Morifumi Ohno, Yuuji Saegusa, Hiro Tajima, Osamu Tajima, Tomiaki Takahashi,
Susumu Terada, Yoshinobu Unno, Yutaka Ushiroda and Gary Varner, Proceedings of the 15th
International Workshop on Vertex Detectors: Perugia, Italy, Sep., 2006, Nucl. Instr. and Meth. A. Vol. 582,
Issue 3, Dec. 2007, Pages 861-865, http://dx.doi.org/10.1016/j.nima.2007.07.130,
14 "Radiation Resistance of SOI Pixel Sensors Fabricated with OKI 0.15µm FD-SOI Technology", K. Hara, M.
Kochiyama, A. Mochizuki, T. Sega, Y. Arai, K. Fukuda, H. Hayashi, M. Hazumi, J. Ida, H. Ikeda, Y.
Ikegami, H. Ishino, Y. Kawai, T. Kohriki, H. Komatsubara, H. Miyake, M. Ohno, M. Okihara, S. Terada, T.
Tsuboyama, Y. Unno, N04-5, Nuclear Science Symposium Conference Record, 2008. NSS '08. IEEE,
19-25 Oct. 2008 Page(s):1369 _ 1374, Digital Object Identifier 10.1109/NSSMIC.2008.4774670, IEEE
Transactions on Nuclear Science, Volume 56, Issue 5, Part 2, Oct. 2009 Page(s):2896 - 2904.
15 "Development of Silicon-on-Insulator Sensor for X-Ray Free-Electron Laser Applications",T. Kudo, T.
Hatsui, Y. Arai, Y. Ikegami, Y. Unno, T. Tsuboyama, S. Terada, M. Hazumi, T. Kohriki, H. Ikeda, K. Hara,
A. Mochizuki, H. Miyake, H. Ishino, Y. Saegusa, S. Ono, M. Ohno, K. Fukuda, H. Komatsubara, J. Ida, H.
Hayashi, Y. Kawai, M. Okihara, T. Ishikawa, IEEE Nucl. Sci. Symp., Oct. 2008, Poster R12-58,
16 "Waveform Observation of Digital Single-Event Transients Employing Monitoring Transistor Technique",Daisuke Kobayashi, Kazuyuki Hirose, Yoshimitsu Yanagawa, Hirokazu Ikeda, Hirobumi Saito, V´eroniqueFerlet-Cavrois, Dale McMorrow, Marc Gaillardin, Philippe Paillet, Yasuo Arai, and Morifumi Ohno,IEEE
Trans. Nucl. Sci., Volume 55, Issue 6, Part 1, Dec. 2008 Page(s):2872 _ 2879, Digital Object
Identifier 10.1109/TNS.2008.2006836.
17 "High-speed charge-to-time converter ASIC for the Super-Kamiokande detector, H. Nishino, K. Awai, Y.
Hayato, S. Nakayama, K. Okumura, M. Shiozawa, A. Takeda, K. Ishikawa, A. Minegishi, Y. Arai,
Nucl.Instrum.Meth.A610:710-717,2009.
18 "Device-physics-based analytical model for single event transients in SOI CMOS logics”,D. Kobayashi, K.
Hirose, V. Ferlet-Cavrois, D. McMorrow, M. Gaillardin, T. Makino, H. Ikeda, Y. Arai, and M. Ohno,, 2009
IEEE Nuclear and Space Radiation Effects Conference (NSREC), Quebec, Canada, July 20--24, IEEE
Trans. Nucl. Sci. 56 (2009) 3043.
19 "Developments of SOI Monolithic Pixel Detectors", Y. Arai, T. Miyoshi, Y. Unno, T. Tsuboyama, S. Terada,
Y. Ikegami, T. Kohriki, K. Tauchi, Y. Ikemoto, R. Ichimiya, H. Ikeda, K. Hara, H. Miyake, M. Kochiyama, T.
Sega, K. Hanagaki, M. Hirose, T. Hatsui, T. Kudo, T. Hirono, M. Yabashi, Y. Furukawa, G. Varner, M.
Cooney, H. Hoedlmoser, J. Kennedy, H. Sahoo, M. Battaglia, P. Denes, C. Vu, D. Contarato, P. Giubilato,
L. Glesener, R. Yarema, R. Lipton, G. Deptuch, M. Trimpl, M. Ohno, K. Fukuda, H. Komatsubara, J. Ida,
M. Okihara, H. Hayashi, Y. Kawai, A. Ohtomo, , Technology and Instrumentation in Particle Physics 2009
in Tsukuba, Japan, 11-17 March, 2009, Nucl. Instr. and Meth. A 623(2010)186-188,
doi:10.1016/j.nima.2010.02.190
20 "Silicon-on-insulator technology enables next-generation radiation image sensors", Yasuo Arai and
Toshinobu
Miyoshi,August2009,
SPIE
Newsroom.
http://spie.org/x36212.xml?highlight=x2414&ArticleID=x36212,DOI:10.1117/2.1200907.1725.
21 "Development of SOI Pixel Process Technology",Y. Arai, T. Miyoshi, Y. Unno, T. Tsuboyama, S. Terada,
Y. Ikegami, R. Ichimiya, T. Kohriki, K. Tauchi, Y. Ikemoto, R. Ichimiya, Y. Fujita, T. Uchida, H. Ikeda, K.
Hara, H. Miyake, M. Kochiyama, T. Sega, K. Hanagaki, M. Hirose, J. Uchida, Y. Onuki, Y. Horii, H.
Yamamoto, T. Tsuru, H. Matsumoto, S. G. Ryu, R. Takashima, A. Takeda, H. Ikeda, D. Kobayashi, T.
Wada, H. Nagatg, T. Hatsui, T. Kudo, A. Taketani, T. Kameshima, T. Hirono, M. Yabashi, Y. Furukawa,
M. Battaglia, P. Denes, C. Vu, D. Contarato, P. Giubilato, T. S. Kim, T. Hatsui, T. Kudo, T. Hirono, M.
Yabashi, Y. Furukawe, M. Ohno, K. Fukuda, I. Kurachi, H. Komatsubara, J. Ida, M. Okihara, N. Kuriyama,
M. Motoyoshi, 7th International "Hiroshima" Symposium on Development and Applications of
Semiconductor Tracking Devices, Hiroshima, Japan, Aug. 29-Sep.1, 2009, Nucl. Instr. and Meth.
doi:10.1016/j.nima.2010.04.081. Vol. 636, Issue 1, Supplement, 2011, Pages S31-S36.
22 "Reduction techniques of the back gate effect in the SOI Pixel Detector",R. Ichimiya, Y.Arai, K. Fukuda, I.
Kurachi, N. Kuriyama, M. Ohno, M. Okihara, for the SOI Pixel collaboration,Proceedings of Topical
Workshop on Electronics for Particle Physics (TWEPP-09), 21-25 Sep. 2009, CERN-2009-006, pp. 68-71.
3423 "New Techniques in SOI Pixel Detector",Y. Arai, 2009 IEEE Nuclear Science Symposium and Medical
Imaging Conference, Orlando Florida, Oct. 25-31, 2009, Conference Record, N22-2, pp. 1161-1164.
Digital Object Identifier: 10.1109/NSSMIC.2009.5402397
24 "Vertical Integration of Radiation Sensors and Readout Electronics",Y.Arai,15th MediterranianElectromechanical Conference, Melecon 2010, Valletta, Malta, 25-28 April, 2010, pp. 1062-1067.
25 "Integrated Radiation Image Sensors with SOI technology", Yasuo Arai, Toshinobu Miyoshi, Ryo Ichimiya,
Kazuhiko Hara, Yoshiyuki Onuki, SOI Conference (SOI), 2010 IEEE International Digital Object Identifier:10.1109/SOI.2010.5641403, Publication Year: 2010 , Page(s): 1 - 5.
26 "Readout ASIC With SOI Technology for X-Ray CCDs", Kishishita, T.; Idehara, T.; Ikeda, H.; Tsunemi, H.;
Arai, Y.; Sato, G.; Takahashi, T.;, Nuclear Science, IEEE Transactions on Volume: 57 , Issue: 4 , Part: 2,
Digital Object Identifier: 10.1109/TNS.2010.2049371, Publication Year: 2010 , Page(s): 2359 - 2364.
27 "Large SET Duration Broadening in a Fully-Depleted SOI Technology-Mitigation With Body Contacts",
Ferlet-Cavrois, V.; Kobayashi, D.; McMorrow, D.; Schwank, J. R.; Ikeda, H.; Zadeh, A.; Flament, O.;
Hirose, K.;, Nuclear Science, IEEE Transactions on Volume: 57 , Issue: 4 , Part: 1, Digital Object
Identifier: 10.1109/TNS.2010.2048927, Publication Year: 2010 , Page(s): 1811 - 1819.
28 "Development of INTPIX and CNTPIX Silicon-On-Insulator Monolithic Pixel Devices", K. Hara, M.
Kochiyama, K. Koike, T. Sega, K. Shinsho, Y. Arai, Y. Fujita, R. Ichimiya, Y. Ikegami, Y. Ikemoto, T.
Kohriki, T. Miyoshi, K. Tauchi, S.Terada, T. Tsuboyma, Y. Unno, Y. Horii, Y. Onuki, D. Nio, A. Takeda,
K.Hanagaki, J. Uchida, T. Tsuru, S.G. Ryu, I. Kurachi, H. Kasai, N. Kuriyama, N.Miura, M. Okihara, M.
Motoyoshi,
VERTEX
2010,
Loch
Lomond,
UK,
June,
2010,
http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=113, PoS(VERTEX 2010)033.
29 "Development of X-ray Imaging Spectroscopy Sensor with SOI CMOS Technology", Syukyo Gando Ryu,
Takesahi Go Tsuru, Shinya Nakashima, Yasuo Arai, Ayaki Takeda, T. Miyoshi, R. Ichimiya, Y. Ikemoto, R.
Takashima d, T. Imamura, T. Ohmoto, and A. Iwata, 2010 IEEE Nuclear Science Symposium,
Conference record. doi: 10.1109/NSSMIC.2010.5873714, 2010 , Page(s): 43-48.
30 "Evaluation of Monolithic Silicon-On-Insulator Pixel Devices Thinned to 100 um", K. Shinsho, K. Hara, Y.
Arai, Y. Ikemoto, T. Kohriki, T. Miyoshi, 2010 IEEE Nuclear Science Symposium, Conference record, doi:
10.1109/NSSMIC.2010.5873838, 2010, Page(s): 646-649
31 "Radiation test on FD-SOI Readout ASIC of Pair-monitor for ILC", Yutaro Sato , Yasuo Arai, Hirokazu
Ikeda, Tadashi Nagamine, Yosuke Takubo, Toshiaki Tauchi, Hitoshi Yamamoto, Nucl. Instr. and Meth.
A(2011), doi:10.1016/j.nima.2010.12.149, Volume 650, Issue 1, 11 September 2011, Pages 106-110.
32 "Performance study of SOI monolithic pixel detectors for X-ray application", T. Miyoshi, Y. Arai, M. Hirose,
R. Ichimiya, Y. Ikemoto, T. Kohriki, T. Tsuboyama, Y. Unno, 7th International "Hiroshima" Symposium on
Development and Applications of Semiconductor Tracking Devices, International Conference Center
Hiroshima, Japan, Aug. 29-Sep.1, 2009, Nucl. Instr. and Meth. A, doi:10.1016/j.nima.2010.04.117, Vol.
636 (2011)pp. S237-S241.
33 "Radiation effects in silicon-on-insulator transistors with back-gate control method fabricated with OKI
Semiconductor 0.20 µm FD-SOI technology",M. Kochiyama, T. Sega, K. Hara, Y. Arai, T. Miyoshi, Y.
Ikegami, S. Terada, Y. Unno, K. Fukuda, M. Okihara, Nucl. Instr. and Meth. A(2010),
doi:10.1016/j.nima.2010.04.086, Volume 636, Issue 1, Supplement, 21 April 2011, Pages S62-S67.
34 "SOI Readout ASIC of Pair-monitor for International Linear Collider",Yutaro Sato, Yasuo Arai, Hirokazu
Ikeda, Tadashi Nagamine, Yosuke Takubo, Toshiaki Tauchi, Hitoshi Yamamoto, Nuclear Inst. andMethods in Physics Research, A10.1016/j.nima.2011.02.063, Vol. 637, Isuue 1, May 2011, pp. 53-59.
35 "Tests of monolithic pixel detectors in SOI technology with depleted substrate", Piero Giubilato, MarcoBattaglia, Dario Bisello, Devis Contarato, Peter Denes b, Tae Sung Kim,Serena Mattiazzo, Devis Pantano,NicolaPozzobon,
C.S.Tindall,
Sarah
Zalusky,
Nucl.Instr.andMeth.
A(2010),
doi:10.1016/j.nima.2010.11.185,
36 "Monolithic pixel detectors in a deep submicron SOI process",Grzegorz Deptuch,Nuclear Instruments andMethods in Physics Research A623(2010)183_185,37 "First Performance Evaluation of an X-Ray SOI Pixel Sensor for Imaging Spectroscopy and Intra-Pixel
Trigger",Syukyo Gando Ryu, Takeshi Go Tsuru, Shinya Nakashima, Ayaki Takeda,Yasuo Arai,
Toshinobu Miyoshi, Ryo Ichimiya, Yukiko Ikemoto, Hironori, Matsumoto, Toshifumi Imamura, Takafumi
Ohmoto, and Atsushi Iwata, IEEE Transactions on Nuclear Science, Vol. 58, No. 5, Oct. 2011, pp.
2528-2536, ISSN: 0018-9499, Digital Object Identifier: 10.1109/TNS.2011.2160970
38 "Development of Cryogenic Readout Electronics for Far-Infrared Astronomical Focal Plane Array",Hirohisa NAGATA, Takehiko WADA, Hirokazu IKEDA, Yasuo ARAI, Morifumi OHNO, Koichi NAGASE,
IEICE
TRANSACTIONSon
Communications,
Vol.
E94-B
No.11,
pp.2952-2960,2011,http://search.ieice.org/bin/summary.php?id=e94-b_11_2952&category=B&year=201
1&lang=E&abst=,
35

39 "SOI detector developments", Y. Onuki, H. Katsurayama,Y. Ono, H. Yamamoto, Y. Arai, Y. Fujita, R.
Ichimiya, Y. Ikegami, Y. Ikemoto, T. Kohriki, T. Miyoshi, K. Tauchi, S. Terada, T. Tsuboyama, Y. Unno, T.
Uchida, K. Hara, K. Shinsho, A. Takeda, K. Hanagaki, T. G. Tsuru, S.G. Ryu, S. Nakashima, H.
Matsumoto, R. Takashima, H. Ikeda, D. Kobayashi, T. Wada, T. Hatsui, T. Kudo, A. Taketani, K.
Kobayashi, Y. Kirihara, S. Ono, M. Omodani, T. Kameshima, Y. Nagatomo, H. Kasai, N. Kuriyama, N.
Miura, M. Okihara, The 20th Anniversary International Workshop on Vertex Detectors - VERTEX 2011,
June 19 - 24, 2011, Rust, Lake Neusiedl, Austria, Proceedings of Science, PoS(Vertex 2011)043.
40 "SOI Pixel Technology",Y. Arai, The 8th international "Hiroshima" Symposium on the Development andApplication of Semiconductor Tracking Detectors (HSTD-8) , Dec. 5-8, 2011, Taipei, Invited Talk.
41 "Development
of
Low
Power
Cryogenic
Readout
Integrated
Circuits
Using
Fully-Depleted-Silicon-on-Insulator CMOS Technology for Far-Infrared Image Sensors", T. Wada, H.
Nagata, H. Ikeda, Y. Arai, M. Ohno and K. Nagase,Journal of Low Temperature Physics, Issn: 0022-2291,
2012,DOI:10.1007/s10909-012-0461-6, http://www.springerlink.com/content/j7306844556t5397/,
42 "Development of an SOI analog front-end ASIC for X-ray charge coupled devices", Tetsuichi Kishishita,
Goro Sato, Hirokazu Ikeda, Motohide Kokubun, Tadayuki Takahashi, Toshihiro Idehara, Hiroshi Tsunemi,
Yasuo Arai, Nuclear Instruments and Methods in Physics Research Section A: Accelerators,
Spectrometers, Detectors and Associated Equipment, Volume 636, Issue 1, Supplement, 21 April 2011,
Pages S143-S148.
43 "X-Ray Detector Activities in Japan", DOE Basic Energy Science Neutron and Photon Detector W.S.,@Gaithersburg, Invited Talk, 2012.8.1, Yasuo Arai.
44 "Advanced Radiation Image Sensors with SOI Technology", Yasuo Arai, Sep. 25, 2012, IEEE Solid
State Device and Materials, Kyoto, Invited Talk.Extended abstract, J-1-1, pp. 1107-1108.
45 “Progress of SOI Pixel Process”, Y. Arai, International Workshop on Semiconductor Pixel Detectors for
Particles and Imaging, September 3 – 7, 2012 in Inawashiro, Japan, Invited Talk.
46 "High-Resolution Monolithic Pixel Detectors in SOI Technology", Oral, T. MIYOSHI, Y. ARAI, I. M.
AHMED, P. KAPUSTA, R. ICHIMIYA, Y. IKEMOTO, Y. FUJITA, K. TAUCHI, A. TAKEDA, International
Workshop on Semiconductor Pixel Detectors for Particles and Imaging (PIXEL2012), Inawashiro, Japan.
47 "High Resolution X-ray Imaging Sensor with SOI Technology", poster, A. TAKEDA, Y. ARAI, T. MIYOSHI,
M. OKIHARA, H. KASAI, N. MIURA, N. KURIYAMA, Y. NAGATOMO, International Workshop on
Semiconductor Pixel Detectors for Particles and Imaging (PIXEL2012), Inawashiro, Japan.
48 "Development of the Pixel OR SOI Detector for High Energy Physics Experiments", Y. Ono, A. Ishikawa,
Y. Arai, T. Tsuboyama, Y. Onuki, A. Iwata, T. Imamura, T. Ohmoto, International Workshop on
Semiconductor Pixel Detectors for Particles and Imaging (PIXEL2012), Inawashiro, Japan. Nuclear
Instruments & Methods in Physics Research A (2013), http://dx.doi.org/10.1016/j. nima.2013.06.044i.
49 "Design and Evaluation of a SOI Pixel Sensor for X-ray Trigger-driven Readout", Ayaki Takeda, Yasuo
Arai, Syukyo Gando Ryu, Shinya Nakashima, Takeshi Go Tsuru,Toshifumi Imamura, Takafumi Ohmoto,and Atsushi Iwata, IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL PP,Issue 99, 2013. DigitalObject Identifier: 10.1109/TNS.2012.2225072.
50 "Tests With Soft X-rays of an Improved Monolithic SOI Active Pixel Sensor", Ryu, S. G.; Tsuru, T. G.;
Prigozhin, G.; Kissel, S.; Bautz, M.; LaMarr, B.; Nakashima, S.; Foster, R. F.; Takeda, A.; Arai, Y.;
Imamura, T.; Ohmoto, T.; Iwata, A. Nuclear Science, IEEE Transactions on Volume:60, Issue: 1, Part:
2,Digital Object Identifier: 10.1109/TNS.2012.2231880, Publication Year: 2013 , Page(s): 465- 469
51 "X-Ray Detection Using SOI Monolithic Sensors at a Compact High-Brightness X-Ray Source Based on
Inverse Compton Scattering", Oral, T. Miyoshi, Y. Arai, M. Fukuda, J. Haba, H. Hayano, Y. Honda, K.
Sakaue, H. Shimizu, A. Takeda, J. Urakawa, K. Watanabe, 2012 IEEE Nuclear Science Symposium,
Anaheim, CA, USA. Nov. 2012.
52 "Monolithic pixel detectors with 0.2 um FD-SOI pixel process technology", Oral, T. MIYOSHI, Y. ARAI, Y.
IKEMOTO,Y. UNNO, Y. IKEGAMI, R. ICHIMIYA, Y. FUJITA, K. TAUCHI, T. TSUBOYAMA, A. TAKEDA,
T. TSURU, S. NAKASHIMA, G. S. RYU, T. KOHRIKI, 13th Vienna Conference on Instrumentation(VCI2013), Vienna, Austria. Nuclear Instruments & Methods in Physics Research A (2013),
http://dx.doi.org/10.1016/j. nima.2013.06.029.
53 Development of a built-in Analog-to-Digital Converter for a X-ray Astronomy Detector with the SOI CMOS
Technology, S.Nakashima, S.G.Ryu. T.G.Tsuru, Y.Arai, A.Takeda, H.Nakajima, H.Tsunemi, J.P.Doty,
T.Imamura, T.Ohmoto, T.Maeda, A.Iwata, 2011 IEEE Nuclear Science Symposium, Valencia, Spain,
Conf. Rec., Nov. 2011.
54 Progress in Development of Monolithic Active Pixel Detector for X-ray Astronomy with SOI CMOS
Technology, S.Nakashima, S.G.Ryu, T.G.Tsuru, A.Takeda, Y.Arai, T.Miyoshi, R.Ichimiya, Y.Ikemoto,T.Imamura, T.Ohmoto, A.Iwata, Physics Procedia, Vol. 37, 2012, pp.1373-1380, doi: j.phpro.2012.04.100
55 Development and characterization of the latest X-ray SOI pixel sensor for a future astronomical mission,36

S.Nakashima, S.G.Ryu, T.Tanaka, T.G.Tsuru, A.Takeda, Y.Arai, T.Imamura, T.Ohmoto, A.Iwata, Nuclear
Instruments and Methods in Physics Research Section A (NIMA), Vol 731, 2013, pp. 74-78,
doi:j.nima.2013.04.063[Japanese]ĸ ÛÌ·HJąă¹¼ĴõÞįĚî & UĮ÷SÏõKH&/51:/1'1/4:;:1C?'?A7A.-"; 
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[i] SOIPIX collaboration. http://rd.kek.jp/project/soi/. Interdisciplinary research on quantum imaging
opened with 3D semiconductor detector, http://soipix.jp.
[ii] K. Morikawa, Y. Kajita, M. Mitarashi, OKI Technical Review, Issue 196, Vol. 70, No. 4, pp. 60-63,
2003.
[iii] Y. Arai, et al., "Development of SOI Pixel Process Technology", Nucl. Instr. and Meth A.
doi:10.1016/j.nima.2010.04.081. Vol. 636, Issue 1, Supplement, 21 2011, pp. S31-S36.
SOI Pixel collaboration http://soipix.jp.
[iv] A. Takeda, et al., "Design and Evaluation of a SOI Pixel Sensor for X-ray Trigger-driven
Readout", IEEE Trans. on Nucl. Sci., Vol pp, Issue 99, 2013. Digital Object Identifier:10.1109/TNS.2012.2225072.
[v] T. Hatsui, "SOI Pixel Sensor Process",
http://www-ppd.fnal.gov/EPPOffice-W/Research_Techniques_Seminar/talks/Hatsui.pdf[vi] Y. Ono, et al., "Development of the Pixel OR SOI Detector for High Energy Physics Experiments",
Nucl. Instr. & Meth. A, (2013), http://dx.doi.org/10.1016/j. nima.2013.06.044i.
[vii]S. Honda, K. Hara, M. Asano, T. Maeda, N. Tobita, Y. Arai, T. Miyoshi, M. Ohno, T. Hatsui, T.
Tsuru, N. Miura, H. Kasai, M. Okihara, "Total Ionization Damage Effects in Double
Silicon-on-Insulator Devices", IEEE Nucl. Sci. Symposium, Conference Record, N42-2.
[viii] M. Motoyoshi, et al., "Stacked SOI Pixel Detector using Versatile Fine Pitch m-Bump
Technology", IEEE Int. 3D System Integration Conf.2011 (3D-IC), 2012, Session 5-2

38

MPGD PROJECT
UNO, Shoji
INTRODUCTION

We have been developing Micro Pattern Gaseous detector (MPGD) after forming Detector
Technology Project (DTP). KEK group mainly focuses on Gas Electron Multiplier (GEM). At the
beginning, some basic studies (gas gain, charge spread and etc.) were performed tounderstand features of GEM detector [1]. Also, flexible thick GEM was developed together withJapanese local company [2] to get higher gas gain in a single GEM setup [3]. A fine pitch
readout pattern and new high density readout electronics are required to take advantage of
MPGD (imaging capability and high counting rate capability). To do so, we are developing ASIC
and a readout board with FPGA. Then, a compact system was developed [4]. Also, we aretrying to find new applications to new fields. One good application is a neutron detector for pulse
neutron sources like J-PARC. In this document, recent development items are described.

RECENT DEVELOPMENT ITEMS

1 Readout pattern with resistive sheet
One of the important recent achievementsis to realize new two-dimensional readout patternwith a high resistive sheet. Readout of two-dimensional position for one hit point is one of key
items for imaging with MPGD. Although a pulsed MPGD signal should be able to read out using
a simple double side readout strip pattern, we had not succeeded in this method for several
years due to charge up on the front surface of the insulator. In order to avoid the charge up, thehigh resistive sheet was introduced on
the front surface of the readout
pattern. Then, the AC signal canpenetrate the high resistive sheet aswell as the insulator of the readout
pattern. The real charge (DC) can betransferred to ground through theresistive sheet. Fig. 1 shows acorrelation diagram among the pulse
heights for front and rear strips using
a 55Fe radiation source. It is clearlyseen that same amount of charge is
induced in either of the strips. A test
using the neutron beam at MLF of
Fig.1 Correlation diagram between the ADC counts for
J-PARC was also performed showing
the front and the rear strips using the simple double
the promising results.
side readout pattern with the high resistive sheet22 New GEM foils
One serious problem for using GEM detectors is unrecoverable damage caused by a big
discharge. When the damage happens once, the GEM foil should be replaced for operation of
the chamber again. To avoid this problem, the gas gain should be reduced. Also, several new
GEM foils has been developed. One of such GEM foils has resistive electrodes. Even if a small
discharge occurs in one GEM hole, the discharge does not increase. Since large stored charge
does not gather into the hole due to resistivity of electrode. We are developing such GEM foils
and can observe the signal with 55Fe. But, it is not so easy to get the suitable high resistivity
together with suitable etching capability. Other new GEM is to use Teflon instead of Polyamide(PI) or Liquid Crystal Polymer (LCP) as an insulator. The original problem is carbonization on
the surface of the insulator caused by the big discharge. Teflon has good capability against the
carbonization. It means that the serious damage does not realize even for the big discharge.
We are developing such GEM foils and can see the signal with 55Fe. So far, frequent discharges
occur as compared with normal GEM foils. But, there is no serious damage as expected.
Developing status will be presented in coming review meeting.

3 Electronics

The readout electronics is one of key issues of MPGD development. Recently, we developed
two types of readout boards using ASIC and FPGA. One is higher density and higher readout
event rate capability. Another one is to read out more precise data with moderate readout rate.

3-1 256 channels board
Fig. 2 shows a photo of 256 channels readout board. This board is developed to aim higher
density and higher events rate. One ASIC chip contains 32 channels for preamplifier, shaperand discriminator. Then, the digital
output signals send to FPGA. The
100 MHz sampling, coincidence
logic for X-Y strips, data formatting
and data transfer function (TCP/IP)
thorough Ethernet are implemented
in FPGA. Fig. 3 shows data transfer
rate with a test pulse. Maximum
speed (12MHz) is limited by 1 Gbps
Ethernet speed. One board (256channels) matches to 128 channels
for each X and Y strip, whichcorrespond to 0.8 mm pitch strips in
Fig. 2 Photo for 256 channels board. There are 8 ASICs
100×100 mm2 active area. We are
and one FPGA.

3

using this readout board with the GEM chamber for various applications, which are describedlater. Unfortunately, there are some malfunctions in ASIC and the whole 256 channels are notactive. New ASIC chips are under construction and will be available, soon.

Fig.3 Event rate using test pulses with the 256 channels board

3-2 64 channels board
Fig. 4 shows a photo of 64 channels readout board, which is developed very recently. The previous
256 channels readout board can treat digital signals only to get higher event rate. In some cases,
precise measurements for timing and pulse height are required. Therefore, we developed different
readout board, which isoriginally developed forBelle-II
CDC
readout
system. The precise (1nsec timing resolution) TDC
is implemented in FPGA
and 30MHz 10 bit FADCs
are mounted on the board
to measure the pulse height
precisely with moderatechanneldensity(64
channels) and less event
rate (~40 kHz). The datawith this 64 channels board
will be presented in the
coming review meeting.
Fig4. Photo for 64 channels board. There are 6 ASICs, 6 FADCs and one
FPGA.
4APPLICATIONS

1 Neutron detector
We are trying to apply GEM detectors to various fields. One promising application is aneutron detector for the pulse neutron sources like J-PARC. In this case, two dimensional
position and timing information are important to measure incident position and wave length ofeach neutron, respectively. In order to detect thermal and cold neutrons, boron solid convertor
is used instead of expensive helium-3 gas. In this case, the range for emitted charged particles(alpha and lithium nucleus) inside the boron convertor is rather short. Therefore, some ideas
are necessary to improve detection efficiency. One idea is to coat thin boron layer on the both
surfaces of GEM foil and stack several foils in one chamber [5]. Another one is to stack boron
coated plates with many holes. In this case, each hole of several plates should be aligned forionizing electrons to pass through holes and to reach to the final GEM foil for the amplification.
Detail structures will be presented in the review meeting.
Anyway, one simple application to this kind of neutron detectors is a neutron beam monitor,
since high efficiency is not required. Real monitor system has being used for the beam lines of
MLF in J-PARC to calibrate beam intensity each wave length during whole experimental period[6,7]. Other interesting application is a detector for an energy selective neutron radiography,
which are described in following sections.

1-1Resonance absorption
Almost all elements have the resonance cross section for neutrons. Usually in the case ofheavy materials resonance cross sections begin to appear at low energy region around eV orless, and in the case of light materials at higher energy region. So far, relatively low energy
resonances have been used since it is easier to measure than the high energy ones. However,
it is useful to measure the high energy resonances to expand the applicability of the resonancetransmission method. For this, a low noise and high time resolution measurement is required.
Iron is one of the most important materials
and a big resonance exists at 27.7 keV. We try
to measure this resonance by using a GEM-ray background is very low [8].
Fig. 5 is an example of the transmission
spectrum of a SUS sample. Resonance dips
were observed corresponding to Fe, Mn and
Co. Content of iron is about 70%, Mn 2%, andCo is impurity in original Ni; so the content isextremely low. Fig.6 shows a photo of a
SUS304 washer sample and the distributionof each material by using peaks of iron 27.7
Fig.5An example of transmission spectra5keV, Mn 336 eV and Co 135 eV. Here, we succeeded to measure a peak around 30 keV andalso the very low content Co. More results are described in reference [9].

Fig.6 Photo of a washer sample and elemental distributions

1-2Brag edge analysis
Neutron transmission imaging, namely neutron radiography, is one of useful methods to see
inside of objects. The neutron can easily transmit through major metals and see materials
behind or in the metals although the x-ray cannot. Furthermore, energy selective imaging using
a narrower energy band give a much different image from the traditional wide energy band
images. By using a pulsed neutron source, different contrast images reflecting the cross section
structure were obtained by one measurement. Furthermore, an idea to identify materials in an
object was demonstrated at a pulsed neutron source by analyzing the Bragg edge of the eachmaterial. A map of strain was obtained by analyzing the wavelength of Bragg edge. More detailanalysis method and results are described in references [10,11].

2 G amma detector

The conventional gamma cameras using NaI(Tl)/PMT scintillation detector have inherent
limitations in spatial resolution, sensitivity, and detector system is very expensive. Gamma
cameras using GEM have been shown to offer potential improvements in basic performance ascompared with conventional gamma cameras at spatial resolution and system costs. In ourcamera, a solid converter (gold) is used for the detection of gamma-ray [12]. We haveconstructed a small field of view prototype gamma camera with 100mm 100mm GEM foils.
Our system consists of the gamma conversion layers and the amplification layers. The GEM
foils of conversion layer are coated by gold with 3μm thickness on the both surfaces. In order toobtain higher detection efficiency, several gold-coated GEM foils are stacked. Gold-coated
GEM foils were manufactured and a simple test was carried out to confirm the principle. In orderto know the performance of the prototype gamma camera, gamma-ray irradiation test was
6performed with radioactive source of 99mTc (141keV). Two dimensional images were obtainedusing a pinhole collimator as shown in Fig.7. This system enables use of gamma-ray imaging
system in various fields where it has not previously been possible to use such systems. Moreinformation is available in a reference [13]. Recently, this work is not so active due to man
power problem in our group, unfortunately.

99m

Fig.7 (a) Imaging result of a
Tc-filled original resolution phantom constructed from anacrylic disk in which holes of different sizes (0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 mm) were drilled.
(b,c) Holes are clearly visible down to size of 2.5 mm, which sharp signals in the profile line.

Wide spread activities
There are various activities for MPGD development at several universities in Japan. Thoseare basically independent. But, closer communication is important to activate various works. To
do so, we had formed a basic study group to exchange information about basic R&D and also
have organized domestic MPGD workshop in Japan once a year at various universities.
Around 80 people including company persons have joined the workshop and have discusses
various items.
7

SUMMARY

We have been developing new GEM foils and new detectors with new electronics. Some
detectors are already applied for various fields. New GEM foils are promising against thedischarge. New good detectors with high performance will become ready soon.

REFERENCE[1] S.Uno, et al., 2006 IEEE Nuclear Science Symposium Conference Record N16-4,“Study of a Charge Distribution on a Readout Board with Triple GEM Chamber”[2] Scienergy Co. Ltd. (info@scienergy.jp). (http://www.scienergy.jp).
[3] S. Uno, et al., Nuclear Instruments and Methods in Physics Research A 581 (2007) 271-273“Performance study of new thicker GEM”
[4] Tomohisa Uchida, et al., IEEE Trans. Nucl. Sci., vol. 55 No.5 (2008) 2698-2703,“Prototype of a Compact Imaging System for GEM Detectors”[5]S. Uno, et al., Physics Procedia 26 (2012) 142-152,“Two-dimensional Neutron Detector with GEM and its Applications”[6] H. Ohshita, et al., Nuclear Instruments and Methods in Physics Research A 623 (201)126-128,“Development of a neutron detector with a GEM”.
[7] Hidetoshi Ohshita, et al., Nuclear Instruments and Methods in Physics Research A 672(2012) 75-81,“Stability of neutron beam monitor for High Intensity Total Diffractometer at J-PARC”.
[8] S.Uno, et al., Physics Procedia 37 (2012) 600-605,“Development of a two-dimensional gaseous detector for energy-selective neutron
radiography”.
[9] Tesuya Kai, et al., Physics Procedia 43 (2013) 111-120,“Visibility estimation for neutron resonance absorption radiography using a pulsed neutron
source”.
[10] H. Sato, et al., Materials Transactions, Vol.52 No.06 (2011) 1294-1302,“A Rietveld-Type Analysis Code for a Pulsed Neutron Bragg-Edge Transmission Imaging andQuantitative Evaluation of Texture and Microstructure of a Welded Iron”.
[11] K. Kino, et al., Physics Procedia 43 (2013) 360-364,“Analysis of crystallographic structure of a Japanese sword by the pulsed neutron transmission
method”.
[12] Takahisa Koike, et al., Nuclear Instruments and Methods in Physics Research A 648 (2011)180-185,“A new gamma-ray detector with gold-plated gas electron multiplier”.
[13] T. Koike, et al., 2012 JINST 7 C01078,“A new gamma camera with a Gas Electron Multiplier”.

8SCD PROJECT (SUPERCONDUCTING DETECTOR)
HAZUMI, Masashi
INTRODUCTION

Superconducting Detectors (SCDs) are the detectors consisting of superconducting materials.
In the superconductors, Cooper pairs play an essential role in the detection principle; becauseof the small binding energy of Cooper pairs, an order of milli-electron volt, SCD in general hasvery high sensitivity to the electromagnetic waves whose wavelength ranges from millimeter togamma rays. The SCD can be applied to a wide range of fields: particle physics, astronomy,material science, and so on.
There are several kinds of SCDs. Examples are TES (transition edge sensor) bolometer,
MMC (metallic magnetic calorimeter), STJ (Superconducting Tunnel Junction) and KID (Kinetic
Inductance Detector). The SCD group in the KEK Detector Technology Project has beendeveloping mainly STJ and KID. We report on the development status of the SCD in our group.
The SCDs are fabricated using a facility in KEK with a lithography technique. The facility has
been operating from 2009, and contains two sputter machines to form thin layers of metal andinsulator, two etching machines, a yellow room for the development and the patterning, an
optical microscope, a profile meter, a SEM and an AMF. We use a helium-3 sorption refrigerator
able to cool the detectors down to 0.3K for the detector evaluation.

STJ (SUPERCONDUCTING TUNNEL JUNCTION)

The STJ has the Josephson junction of sandwich-like SIS (superconductor insulator
superconductor) structure. The insulator layer is formed with oxide aluminum and has athickness of about 1nm. For the superconductors, we use Hf, Al or a combination of Al and Nb.
The Cooper pair binding energy ( ), which equals to the gap energy in the superconductor, isgiven as, whereis the Boltzmann constant andis the criticaltemperature at which the normal metal transforms to the superconductor. For example, thebinding energy is 0.34 meV = 82 GHz for Al which has
K.

Figure 1: Detection principles of the STJ
9The detection principles of the STJ are shown in Fig. 1. The direct Cooper pair breaking canbe caused by a photon or a phonon with the energy greater than the binding energy,
generating quasi-particles. The quasi-particles can penetrate the insulator layer by tunneling.
The second principle is called the photon associated tunneling. An electron in the valence band
can jump to the conducting band through tunneling by the assist of a photon and the bias
voltage applied to the SIS junction. In this case, the photon with energy greater thancan be detected, whereis the bias voltage. Therefore the STJ can in principle directly detectphotons with energies less than. This is one of the advantages of the STJ since the STJ can
detect millimeter wave photons with frequencies less than 82 GHz by using Al, while the KID
cannot. Other advantages of the STJ include the large dynamic range of 106, the fast responseof order of micro-seconds, and no need of the fine temperature control below 0.6 K for Nb/Al
STJs compared with the TES bolometers.
We have been developing STJs for detections of millimeter waves and infrared photons. The
former is for cosmic microwave background detection and the latter is for the detection ofphotons from the decays of cosmic neutrinos.

2-1 The STJ for millimeter waves
At the first stage, we developed PCTJ (parallel connected twin junction) detector. The twin
parallel STJs and the inductance induced by the microstrip line between the STJs form aresonant circuit. The circuit can accumulate the millimeter wave energy that breaks Cooper
pairs. We successfully took a picture as shown in Fig. 2 with 90GHz millimeter waves. We,
however, found that the control to tune the resonant frequencies is not easy due to thefabrication.

Figure 2: (Left) Metal mask on the polyethylene substrate. (Right) Picture taken by asingle antenna-coupled PCTJ detector using the mask with 90GHz millimeter waves.
The mask was moved by 1mm step in the xy plane.

Instead we have designed a microstrip transmission type STJs shown in Fig. 3. The
log-periodic antenna has a capability to receive a broad bandwidth with the impedance
independent of frequencies. The lower frequency limit is determined by the size of the antenna.

10

The strip line passes the millimeter waves
received by the antenna to both sides where the
STJs are located. The STJ has a microwave
transmission type structure, where certain
resonant frequency waves are confined with acondition of, whereis the length of
the transmission type STJ (with
thewidth),
is an integer number andis the wavelength of the resonant wave. Figure 4
shows the observed resonant frequencies as afunction of a normalized length defined as 2 ,where. We found that the STJs withhave the resonant frequencies ofnormalized lengths from 1 to 6, while the STJs
withhave only resonant frequenciesof even integer numbers of normalized lengths,
implying that the transmission type STJ has theresonances with the condition of.
From the slope, we can estimate the groupvelocity to be 0.03c, where c is the velocity oflight in vacuum, in agreement with the expectedvalue estimated assuming the insulator
thickness (1nm) and the London penetration
length.
Figure 5 shows the ratio of the leakage
current to 4.2K as a function of temperature forthe fabricated Nb/Al STJ. The ratios are inagreement with the BCS theory predictions. The
level of 10-6 at 0.8K is the one of the best ratios
in the world. The reason for the deviation fromthe BCS theory below 0.8K is not clear yet, but
theimaginarycontributionofthesuperconducting gap energy can explain it.
Since the STJ noise is dominated by the shotnoise of the leakage current, the intrinsic noise
does not change below 0.8K.

Figure 3: Structure of microstrip transmission
type STJs coupled to the antenna.

Figure 4: Resonant frequencies as afunction of the normalized length.

Figure 5: Ratio of the leakage current to 4.2K
as a function the temperature.
112-2 The Hf STJ for the infrared photon detection
The primary purpose of the development of Hf STJs is to detect infrared photons emitted fromthe decays of cosmic neutrinos. The energy of photons is estimated to be 25meV from the factthat the neutrino mass lower limit is determined from neutrino oscillation measurements. To
distinguish from the infrared backgrounds, the detector has to have the energy resolution of 2%.
This requirement is satisfied by using Hf STJs. The group at University of Tsukuba has beendeveloping Hf STJs. Figure 6 shows the IV curves of the fabricated Hf STJ. As shown in the
figure, the Josephson current is suppressed by applying a magnetic field, implying the SIS
junction is formed correctly. Figure 7 shows a response of the Hf STJ to the laser light. This may
be the first time to see the signals of the Hf STJ.

2-3 The Nb/Al STJ on the SOI (Silicon On Insulator).
The cryogenic amplification of signals from STJs is critical to detect the photons from theneutrino decays. The group from University of Tsukuba has started developing Nb/Al STJs on
the SOI. The SOI comprises of the CMOS circuits in which the signal can be amplified at thecryogenic temperature of 0.3K. The fabrication procedure has been established. Performanceof the STJ and the SOI is being tested.

Figure 6: IV curves of the Hf STJ. The Josephson current of the Hf STJ is seen in the left figure, andthe current is suppressed when we apply a magnetic field (right figure).

12

Figure 7: Laser pulse response of the Hf STJ. Top line shows the output current of the Hf STJ.
Middle is laser pulse trigger timing.

KID (KINETIC INDUCTANCE DETECTOR)

Superconductors in general have the kinetic inductance that arises from the total kinetic
energy of Cooper pairs. When energy is deposited to the superconductor and some Cooper
pairs are broken, the net kinetic energy, hence the kinetic inductance, is changed. If we form aresonator with the superconductor, the Cooper pair breaking causes the change of the resonant
frequency. KIDs make use of this mechanism to detect the deposit energy of photons orphonons. The features of the KID are: (1) frequency domain multiplexing, enabling us toreadout hundreds of resonators with a single cable, (2) a simple structure consisting of a single
or double metal layer(s) and (3) needlessness of the bias.
We have been developing KIDs for detections of phonons, optical photons and millimeterwaves. The phonon detection aims to detect dark matter and X-rays in the substrate. The
optical photon detection may be applied to a liquid-helium TPC to detect UV scintillation
photons. The millimeter wave detection is for the CMB polarization measurements.

13

3-1 Phonon detection with the KID
Figure 8 shows the KID design and detected athermal phonon signals of alpha particles
injected into the Si substrate from an 241Am source. The KID consists of meander-likeresonators capacitively coupled to the feed-line. The resonators, feed-line and ground plane are
made of Nb with the thickness of 200nm. Each combination of two resonators has a common fin(0.1x0.3 mm2) made of Al, where phonons from the substrate are detected. From the phonon
signal delays and the distance of the fins, we roughly estimate the propagation speed ofathermal phonons to be 1.1~1.3 km/s

Figure 8 (top left) Configuration of the alpha particle injection, (bottom left) KID design for the detectionof phonons, (right) phonon signals of three combinations of resonators shown in left lower figure.

143-2 Photon detection with Lumped Element KIDs.
We have also been developing Lumped Element KIDs (LEKIDs) for the detection of not only
athermal phonons from the substrate but also visible photons. The detection of visible photons
is usable for the performance evaluation in terms of the responsivity and the response time. We
evaluate Nb LEKIDs using a system consisting of a liquid helium cryostat, a vacuum pump tocool the liquid helium to 1.6K and an optical fiber that introduces the laser light from room
temperature to the LEKIDs in the cryostat (Fig. 9). We use a 660nm semiconductor laser which
can emit 10nsec pulses. Figure 10 shows the LEKID responses to various photon intensities.
The numbers of expected photons are estimated using a photo-multiplier. In principle, theLEKID should have sensitivity to a single photon. We will implement a HEMT amplifier in thesystem soon to increase the sensitivity.

Figure 9: Photon detection system using liquid helium cryostat.

15

Figure 10: LEKID responses for the inputs of various numbers of photons.

3-3 KIDs for the millimeter wave detection
We have been developing antenna-coupled KIDs to detect millimeter waves in the wide
frequency range from 60 to 250GHz. The wide frequency range detection is required to remove
foregrounds for the CMB B-mode detection. Our approach is to use a sinuous antenna which isable to detect dual polarization and cover the wide frequency range. With the frequency filters,
we can design a multichroic detector with a single antenna. We use Nb for the resonators andantennas, and Al for the sensitive region located at the position where the resonant microwave
current becomes maximal in the resonator CPW line (Fig.11). The combination of two metals
enable us to detect the frequency range from 82 to 650GHz, where the lower limit is the energy
threshold to break Cooper pairs in Al, and the upper limit is due to the Cooper pair breaking in
Nb. We successfully fabricated the Nb/Al KIDs and obtain the Q-values of 105 to 106 at 0.3K
(Fig. 11).

16

Figure 11 (left) KID design showing the sinuous antennas coupled to the resonators,(right)Q-values as a function of the temperature.

3-4 A KID readout system
The multiplexing readout system is being developed using a Kintex-7 FPGA board DSP kit
available commercially. With the help from Open-It, we have been developing firmware codesthat generate a frequency comb for the KID resonator excitation and generate I/Q signals foreach resonator (Fig. 12). We have confirmed a successful performance of simultaneous
readout with 32 channels at a sampling rate of 1kHz. Because of the capacity of thelook-up-table in the FPGA chip and the digital signal timing limitation, we expect the 100
channel readout at maximal.

Figure 12: (Left) Kintex-7 FPGA board we are using. (Right) Block Diagram of thegeneration of a frequency comb and I/Q signals with the homodyne readout.

17

DEVELOPMENT HISTORY

2006.12: Proposal of Hf STJ (S. Kim, Tsukuba University)
2007.4: Proposal of Al STJ (M. Hazumi, KEK)
2007.5: STJ group was formed.
2008.12: KEK clean room started operation for the STJ fabrication.
2009.2: Nb/Al STJs were fabricated at KEK first time.
2009.8: Fabrication of Hf SIS structure and set up the dilution refrigerator at TU
2009.8: Detection of millimeter waves with antenna-coupled STJ for 77K radiation
2009.12: Detection of photon assisted tunneling with Nb/Al antenna STJs
2010.3: Imaging with 90GHz with Nb/Al antenna STJs
2010.4: SCD group was formed.
2010.2: KID development started
2010.8: Microstrip transmission STJ development started
2010.11: Detection athermal phonons from the substrate with Al-STJs
2011.1: Detection of 96GHz millimeter waves with antenna-coupled KID
2011.2: Eight channel KID readout with FPGA-based readout system
2011.2: Fabrication of microstrip transmission STJs
2011.3: Earthquake
2011.12: Fabrication of STJs with the lowest leak current in the world
2011.12: Fabrication of Hf STJ and observation of the Josephson current
2012.3: Detection of millimeter waves with microstrip transmission STJs using FTS
2012.8: Detection of athermal phonons from the substrate with Al/Nb KIDs.
2012.12: Fabrication of Nb/Al KIDs with an insertion method
2013.3: Detection of photons with LEKIDs.
2013.3: First Ph.D for S. Mima for the development of the microstrip transmission STJs.
2013.4: Detection of photons with Hf STJs.
2013.4: Proposal of STJs on SOI.
2013.5: Nb/Al KIDs with the Q-value of 106.
2013.6: 16 channel KID readout

18

MEMBERS

Name

affiliation

works

M. Hazumi

KEK

KIDs for CMB, maintenance of the clean room

M. Yoshida

KEK

KIDs for CMB

N. SatoKEK

maintenance of the clean room

H. Watanabe

SOKENDAIKIDs for CMB

H. Ishino

Okayama U.

KIDs for phonon, photon, CMB

Y. KibeOkayama U.

KID readout

A.Kibayashi

Okayama U.

KID fabrication

Y. Yamada

Okayama U.

KIDs for DM

N. Okamoto

Okayama U.

KID fabrication, design for CMB and DM

S. H. Kim

Tsukuba U.

STJs for neutrino decays

Y. Takeuchi

Tsukuba U.

STJs for neutrino decays

K. Kikuchi

Tsukuba U.

STJs for neutrino decays

S. Kanai

Tsukuba U.

STJs for neutrino decays

K. Nagata

Tsukuba U.

STJs for neutrino decays

K. Kasahara

Tsukuba U.

STJs for neutrino decays

R. Ichimura

Tsukuba U.

STJs for neutrino decays

T. Okudaira

Tsukuba U.

STJs for neutrino decays

R. Senzaki

Tsukuba U.

STJs for neutrino decays

K. Moriuchi

Tsukuba U.

STJs for neutrino decays

S. Mima

RIKEN

KIDs for CMB

C. Otani

RIKEN

KIDs for CMB

REVIEWERS

Yutaro Sekimoto

NAOJ

Satoshi Kohjiro

AIST

19

DISSERTATIONSPhD:Satoru Mima, Okayama University, Mar. 2013, ``Development of Microstrip Transmission
Type STJs for the millimeter/sub-millimeter astronomy.''Master of science:
Kazuki Nagata, University of Tsukuba, Feb. 2013, ``Development of Hf STJs for detections ofphotons from the neutrino decays.''

Shinya Kanai, University of Tsukuba, Feb. 2013, ``Development of Nb STJs for the detectionsof infrared photons.''

Taiki Yuasa, Okayama University, Feb. 2013, ``Development of Microwave Kinetic
Inductance Detectors with the combination of Nb and Al.''

Kenji Kiuchi, University of Tsukuba, Feb. 2011, ``Development of Hf STJs having the highenergy resolution.''Noriko Ogura, Okayama University, Feb. 2011, ``Design of Microwave Kinetic Inductance
Detectors using a simulation.''H. Jing, University of Tsukuba, Feb. 2010, ``Development of Hf STJs for far-infrared
photons.''

Ken-ichi Takemasa, University of Tsukuba, Feb. 2009, ``Development of Hf STJs for thedetection of photons from neutrino decays.''

PUBLICATIONS[1]``MKID and its application to cosmology and particle physics'', H. Ishino, M. Hazumi, A.
Kibayashi, Y. Kibe, S. Mima, N. Sato, M. Yoshida and H. Watanabe, IEICE Technical Report
SCE2012-22, 17 (2013).

[2]``Development of Microwave Kinetic Inductance Detectors and their Readout System for
LiteBIRD'', K. Hattori et al., in press in NIMA.
20[3]``Development of Superconducting Detectors'', H. Ishino, M. Hazumi, S. Mima and M.
Yoshida, High energy news, Vol. 32, Number 1, pp.24-33 (2013).

[4]``Development of Superconducting Detectors for Measurements of Cosmic Microwave
Background, K. Hattori et al., Phys. Proc. 37, pp.1406 - 1412 (2012).

[5]``Novel Frequency-Domain Multiplexing MKID Readout for the LiteBIRD Satellite'', J. of
Low Temp. Phys., 167, Issue 5, pp.671 - 677 (2012).

[6]``Development of Superconducting Tunnel Junction Photon Detector using Hafnium'',
S.H. Kim, H.S. Jeong, K. Kiuchi, S. Kanai, T. Onjo, K. Takemasa, Y. Takeuchi, H. Ikeda, S.
Matsuura, H. Sato, M. Hazumi and S.B. Kim., Phys. Proc. 37, pp.667-674 (2012).

PRESENTATIONS``MKID and its application to cosmology and particle physics'', H. Ishino, Workshop for thesuperconducting electronics, Tohoku University, Sendai, Japan, Oct. 2nd, 2013.

“Search for Cosmic Background Neutrino Decay with STJ detectors” Y. Takeuchi, MKID
and Cosmology Workshop @FNAL, Aug. 26-27, 2013,"Search for Cosmic Background Neutrino Decay" S. H. Kim, APPC12 @ Makuhari, July 17,
2013“Development of the Superconducting Detectors for Applications to Particle Physics andAstrophysics” (poster), A. Kibayashi, APPC12, Makuhari, Japan, July14-19, 2013``Development of Microwave Kinetic Inductance Detectors for a detection of phonons'',(poster) H. Ishino, Low Temperature Detectors 15, Pasadena, USA, Jun. 24th, 2013.

``Low Noise Readout System for MKIDs with Frequency-domain Technique towards
application of CMB observation'', (poster) Y. Kibe, Low Temperature Detectors 15, Pasadena,USA, Jun. 24th, 2013.

21

``Hybrid MKIDs with ground-side deposition -- A novel method for microwave detection with aresonator separated from an antenna'', (poster), H. Watanabe, Low Temperature Detectors 15,
Pasadena, USA, Jun. 24th, 2013.

``Transmission line type STJ coupled with a broad band antenna for millimeter andsub-millimeter wave detections'', (poster), S. Mima, CMB2013, OIST, Okinawa, Jun. 2013.

"Search for Cosmic Background Neutrino Decay" (poster) S. H. Kim, SPICA International
Conference 2013 @ University of Tokyo, June 18-21, 2013

"Search for Cosmic Background Neutrino Decay" (poster) Y. Takeuchi, CMB2013,
International Conference on Cosmic Microwave Background Jun. 10-14, 2013 @ OIST,
Okinawa"Development of Superconducting Tunnel Junction Photon Detector on SOI Preamplifier
Board to Search for Radiative Decays of Cosmic Background Neutrino“ (poster) K. Kasahara,
CMB2013, International Conference on Cosmic Microwave Background Jun. 10-14, 2013 @OIST, Okinawa"Development of Nb/Al superconducting tunnel junction detector of a single infrared photon to
search for radiative decay of the cosmic background neutrinos “ (poster) T.Okudaira, :CMB2013, International Conference on Cosmic Microwave Background Jun. 10-14, 2013 @OIST, Okinawa``Development of Microwave Kinetic Inductance Detectors and its Readout System for
LiteBIRD'', (poster), Y. Kibe, VCI2013, Viena, Austria, Feb, 2013.

``Development of Microwave Kinetic Inductance Detector and its Read-out System for
LiteBIRD'', (poster), Y. Kibe, ISSTT2012, Mitaka, Japan, Apr. 2012.

``Novel Frequency-domain multiplexing MKID readout for the LiteBIRD satellite'', (poster), K.
Hattori, LTD14, Heidelberg, Germany, Aug. 2011.

``Development of Superconducting Detectors for Measurements of Cosmic Microwave
Background'', S. Mima, TIPP2011, Chicago, USA, Jun. 2011.

22

``Developments of Aluminum Superconducting Tunnel Junction (STJ) detectors for millimeterwave and particle detections'', (poster), H. Ishino, TIPP2011, Chicago, USA, Jun. 2011.

``Development of Microwave Kinetic Inductance Detectors (MKIDs) for Cosmic Microwave
Background Polarization detection with the LiteBIRD Satellite'', H. Watanabe, The 11th
Workshop on Submillimeter-wave Receiver Technologies in Eastern Asia, Nagoya, Japan, Nov.
2010.

``Development of an Antenna-coupled Al Superconducting Tunnel Junction for a detection of
Cosmic Microwave Background B-mode Polarization'', (poster), H. Ishino, TIPP2009, Tsukuba,
Japan, Mar. 2009.

RESEARCH FUNDS

Grant-in-Aid for Scientific Research on Innovative Areas, S.B. Kim, FY 2013-2017.
Grant-in-Aid for Scientific Research on Innovative Areas, M. Hazumi FY 2009-2013.
Grant-in-Aid for Challenging Exploratory Research, H. Ishino, FY 2012-2013
Grant-in-Aid for Challenging Exploratory Research, H. Ishino, FY 2010-2011
Grant-in-Aid for Young Scientists (A), H. Ishino, FY 2010-2012.
KEK research support program, H. Ishino, FY 2010-2012.
KEK research support program, H. Ishino, FY 2008-2009
KEK research support program, S. H. Kim, FY 2008-2013.

WORKSHOPS``Superconducting Camera and related technology -- Application to the astronomy andcosmology'', KEK, Feb. 20-21, 2009.

23

LIQUID TPC PROJECTLIQUID ARGON TPC
MARUYAMA, Takasumi
SUMMARY OF ACTIVITY DURING 2008-2013

DTP has started the R&D activity on LAr TPC since 2008. This activity is the newest projects
in the DTP.
In 2008, 10L prototype vessel is made to test the readout system for TPCs and to obtain theexperience of the cryogenic system, (Fig.1)

Fig.1 10L test system. Top-right shows the schematic view, and top-left shows a picture of the setup.
Bottom pictures show the TPC inside the inner vessel.

This system consists of an inner vessel, a LAr open bath to cool down, commercial H 2O andO2 filters and vacuum pumps. Inside the inner vessel, hand-made TPC was put as shown in
Fig.1. At the beginning of the test, we use 4ch cupper readout system. The electric field shapers
and anode-grid with stainless wires of 100 m diameter, and 5mm pitch, are made fromstainless plates. Total size of the TPC is 10cm x 10cm x 5 cm. The vacuum evacuation inside
the inner vessel (10-4 Pa level) was performed at first, the cooling down with LAr filled in the24bath and then gas argon is filled inside the inner vessel. Gas argon is liquefied at the end. In
2009, we successfully saw the cosmic ray using the system. Achieved purity is about a few ppb(parts-per-billion) using the set-up.
The latter of 2009, we started the R&D for the 250L system. The primary goal of the R&D is tocheck the detector response of K particles with the beam (J-PARC T32), especially at low
momentum, which is similar to the decay products of the proton decay range. The cryostat(Fig.2, left) was borrowed from the MEG collaboration [1] for the test-beam. In October 2010,
we saw the beautiful tracks of kaons, pions, protons, and positrons. (An example of tracks areshown in right plot in Fig.2 ). During this test-beam for a week, the purity is kept to be around
0.8 ppb with gas recirculation system (it had been slightly degraded during the test-beam).

Fig.2 Left; Schematic view of the 250L system. TPC was made by PC4 circuit board (middle pictures).
Size of the TPC is 40x40x80cm3. The readout plane was 76 ch (1cm/ch) 1D readout, and connected from
TPC to feed-through by twist-flat cables. After the feed-through, electric signal is going to CAEN SY2791
board. Right; one typical tracks (top; pion, middle; positron, bottom; proton)

CAEN high voltage (HV) supplier provides the 9 kV to the cathode plane typically and 12 kV at
maximum. (the drift electric field is 200V/cm typically and 250kV/cm at maximum). There arepossibilities to have sparks in gas argon usually, therefore the gas-tight high voltage
feed-through is important for DC HV system. At anode-grid plane, which is put 1cm below theanode, 1 kV is supplied for typical case, and 2 kV is supplied at maximum case, respectively.
This readout system is crude and 1D, but some preliminary results of the analysis have beenshown in many DTP reviews and international conferences, especially for the DQ/dx analysis[2].
From 2011 to 2012, upgrades of the cryo-systems (especially gas recirculation system), HV
and readout systems have been performed.
Fig.3 shows the upgrade of the gas recirculation and the cryo-system.
25

Fig3; Left; gas recirculation and cryo system in 2010. Right; those in 2012. Gas recirculation system isconnected to “gas pump” in the figures. Green lines correspond to liquid nitrogen system. Liquid argon isstored in the blue tanks, and filled into the inner cryostat via O2 filters. Pictures show O2 filter, cryo-cooler
head, heat exchanger and LAr condenser.

As shown in Fig.3 (green line and dark gray in top-left schematic and bottom middle picture),a cryo-cooler and LN2 coil is put on the top flange of the 250L in 2010. They degraded purity of
LAr due to condensing the dirty gas argon around the coolers. Thus the new gas argon
condenser is inserted into the gas recirculation system, not attached in top flange of the system
directly. To reduce the heat load in the gas recirculation system, the heat exchanger is also
inserted in the system as shown in top-right schematic and bottom-right picture of Fig.3. Due tothe upgrade of the system, the purity is kept to be about 0.3 ppb for a few months. After the
test-beam in 2010, we return the 250L vessel to the MEG collaboration, and we remade thereplica of the 250L cryostat. The LN2 pipes surround the inner vessel of the cryostat, therefore
the pre-cooling can be done more smoothly.
The hand-made O2 filter has been used for direct LAr purification (blue line in schematics in
Fig.3) since 2010. Bottom-left picture in Fig.3 shows the vessel of the filter. Inside the vessel,
the proper size powders of cupper and molecular sieve are filled in. The careful regeneration
procedure is needed in order to use this filter before the operation.
Cockcloft-Walton (CW) circuit is adapted for the high voltage system after 2010 as shown in
Fig.4. CW uses capacitors and diodes in ladders (top drawings in Fig.4) and the only low AC
voltage is needed in the feed-through part. The possibility of the spark in the gas argon is26

reduced. We use 40 stages (1cm/1stage in TPC) for CW system, and each CW stage supply
high voltage to field shaper as shown in the bottom picture in Fig.4. The comparison between
the simulation (LTspice) and the measurement was carefully done (bottom-right). A linearity of
the circuit is kept about a few % level at the final stage at the cathode. Note that the simulation
uses the property of the diode made by the company, and it is essential to make the realistic
result of the simulation. This system successfully supplied the high voltage up to 60 kV. One
caveat is that there is large noise during charging the CW system, therefore we turn off the CW
system after the charging, which takes one minute typically. We recharge the system every 12hours, which cause 5% drop of the cathode voltage.

Fig.4; A drawing of the CW circuit (top). Bottom-left; picture of CW. Bottom-right;
Comparison between simulation (LTspice) and measurements of voltage every five stages.

The readout system is upgraded to 2-dimensional and 4mm pitch using a print circuit board in
2013. Small prototype test was done using 10L system in summer 2012, and a large board wasadapted for the 250L system in 2013. Fig.5 shows the picture and schematic view of the new 2D
readout system. There are number of 1mm x 1mm pads in the plane, and 4 raws and 4 columns
are connected one per each two pads for x and y readout as shown in left schematic view in
Fig.5. This system has an advantage that we can use the same software programs to analyzeboth x-z and y-z planes. However, the readout system has half of the charge compared to thewire readout system since it shares the charge. I.e.; noise level of the detector and readout
system should be minimum to use this kind of system.

27

Fig.5; New readout plane. (bottom-right); picture of the readout plane. (top-right); picture of theboards. Left; schematic which shows the principle of the board.

Fig.6 shows a typical cosmic ray event using all upgrades mentioned above. Top plot shows
the x-z view while the bottom plot shows the y-z view. Vertical axis corresponds to drift timeaxis, and horizontal axis is the x (top) and y (bottom), respectively. Signal-to-noise ratio shouldbe improved, but the first cosmic ray event provides the evidence that the scheme works well.

28

Fig.6; A typical cosmic ray event using 2D readout with 4mm pitches.

REFERENCES[1] S.Mihara et al Nucl. Instrum, Meth. A 518 45 (2004)[2] E.g.; see Masashi Tanaka’s presentation in NNN12.
http://laguna.ethz.ch/indico/getFile.py/access?contribId=38&sessionId=1&resId=0&materialI
d=slides&confId=1

29

PUBLICATIONS (2010-2013)

O.Araoka, et al “A tagged low-momentum kaon test-beam exposure with a 250L LAr TPC(J-PARC T32)” J. Phys. Conf. Ser. 308, 012008 (2011)
M.Tanaka, et al “Recent results from Liquid Argon R&D at KEK” J. Phys. Conf. Ser. 308,
012008 (2011)
T.Maruyama “ R&D towards huge liquid argon detectors for nucleon decay, neutrino
astrophysics and CP-violation in the lepton sector”, AIP Conf. Proc.1222, 117 (2010)
A.Badertscher et al, “A Possible Future Long Baseline Neutrino and Nucleon Decay
Experiment with a 100 kton Liquid Argon TPC at Okinoshima using the J-PARC Neutrino
Facility”, arXiv:0804.2111 [hep-ph].(2008)

TALKS (2010-2013) AT INTERNATION AL CONFERENCES;“Update on LAr TPC Studies in Testbeams in Japan”, T.Maruyama, LAr workshop, Chicago,
USA, 20-21 March 2013.
``Update on LAr TPC Studies in a Testbeam in Japan'', T.Maruyama, 13th International
Workshop on Next generation Nucleon Decay and Neutrino Detectors, Chicago, USA, October
2012.
"J-PARC T32 status and plans" M.Tanaka, 12th International Workshop on Next generation
Nucleon Decay and Neutrino Detectors Crowne Plaza Hotel in Zurich, Switzerland, November 7- 9, 2011"T32@J-PARC results", T.Maruyama, 2nd International Workshop towards the Giant Liquid
Argon Charge Imaging Experiment (GLA2011), Jyvaskyla, Finland”Liquid Argon TPC”, The 2nd Joint Asian Accelerator Workshop (JAAWS), Korea. 2010
“250L”, T.Maruyama, 1st International Workshop towards the Giant Liquid Argon Charge
Imaging Experiment (GLA2010), Tsukuba, Japan, Mar-2010“Recent results from Liquid Argon R&D activity”, M.Tanaka, 1st International Workshop
towards the Giant Liquid Argon Charge Imaging Experiment (GLA2010), Tsukuba, Japan,
Mar-2010”Liquid Argon detector R&D in Japan”, Workshop on Next Generation Nucleon decay and
Neutrino Detectors, Colorado, USA, Oct-2009 (NNN09)”R&D towards Huge Liquid Argon Detectors for Nucleon Decay, Neutrino Astrophysics andCP-violation in the Lepton Sector”, NuFact2009 (11th International Workshop), Chicago, USA,
July-2009”Future of Flavor Physics (T2K)”, Hints for New Physics from Flavor Decays workshop, KEK,
Japan, March-2009.

30

LIQUID XENON TPC
TAUCHI, Toshiaki
INTRODUCTION OF LIQUID XENON TPC R&D

Purpose of this study is a research and development (R&D) of gamma ray detector with highresolutions of the 3 dimensional position and the energy in keV and MeV. The gamma ray
detector can be applied in large fields for the gamma ray astronomy (several 10's keV to several
10's MeV) , experiments of solar neutrino (100keV) , dark matter (10keV), neutrinoless double
beta decay ( 2.48MeV in 136Xe) and medical devises of Single Photon Emission Computed
Tomography (SPECT, several 10 to 300keV ) and Positron Emission Tomography (PET,
511keV).
We chose the technology of time projection chamber (TPC) filled with liquid xenon as an
optimum gamma ray detector for the fast timing signals of scintillation lights and three
dimensional position measurements of charge signals as well as good energy resolution in acompact volume. Our present target is the PET, medical application.
Most of the gamma ray detectors in the medical application are based on scintillation crystals
such as BGO, GSO and LSO. Although these detectors have good resolutions of time andenergy, the spatial resolution is limited by the size of crystals. Especially, the longitudinal
position resolution along the incident gamma ray direction, which is known as DOI (depth ofinteraction) in PET, is about cm.
It produces a large disparity in the PET so that large
statistics, i.e. large radiation dose, is needed to reconstruct good images. Improvement of
DOI resolution is one of major R&D in next generation PET. Silicon micro-strip detectors
provide very precise position resolution. The multilayer detectors have been used forCompton telescope in the gamma ray astronomy. They can be also applied to PET. However,the cost increases for many strip channels, which would be uneconomical.
Compare to them, the liquid xenon TPC (LXeTPC) has all the properties needed for the next
generation PET in principle. The challenges are detection of small charge signals without
amplification, high purification of liquid xenon at ppb level for the charge transformation and thesimultaneous measurements with scintillation lights which have must faster than the charge
signals.
We have started the R&D in 2007. The cryogenics system for the prototype TPC hasconstructed in the first year. We have succeeded to liquefy xenon and fill in the chamber,
May 2008, then the first scintillation signals have been observed with a radiation source in thechamber. In March 2009, we have observed the charge signals with 1cm drift for the first time.
The signals have been detected with 4 anode pads in the 1cm drift TPC prototype, May 2009.
Accumulating the signals of Cosmic rays during summer 2009, a graduate student has reported
the first measurements at JPS, September 2009. Since then, we have been developing thesecond prototype TPC with 5cm drift and 16 pads readout. In parallel, we have started todevelop a frontend electronics based on ASIC chip, 2009.

31

In the world, a few research groups are actively participated in R&D of LXeTPC for PET. We
have been collaborating with a group led by Dominique Thers, Subatech, Nate, France, in theframework of Japan-France cooperation (FJPPL or TYL). Also, we have exchanged graduate
students twice for 2 weeks in January to March 2010 and 3 months in July to December 2013.

FISCAL YEAR OF 2010

A second prototype TPC was tested as shown in Fig.1, where the drift length is 5cm with amesh-type grid in a gap of 1mm in front of anode, and the number of readout PAD channels
increased to 16. An alpha source (241Am, 200Bq) is glued on the cathode and a gamma source(137Cs, 7.34KBq) is put above the anode. The inner diameter of vacuum chamber increased
from 110mm to 148mm accordingly. A getter pump (CapaciTorr D400-2) was installed forbetter purification. Experimentally, the vacuum pressure was significantly improved during thebuild up test for 30 minutes after all the pumps were switched off. However, we could notobserve charge (alpha) signals from 5cm drift for about 2 months circulation. In the meantime,
the frontend electronics was prepared to readout the 16 pad signals. The preamplifier has twoparts, i.e. cold and warm ones. The cold parts consisting of JFET and feedback capacitor andFigure 1: Left photograph shows our setup consisting of the Xe gas circulation system, thechamber of the TPC and the electronics system. Right one shows the TPC with 5cm drift and agrid mesh, where two radiation sources are set at top of the anode (top) and on the cathode(bottom). The anode is segmented into 16 pads of 7.5mm x 7.5mm.

32resistor were installed in the chamber at liquid Xe temperature, while the warm parts are madeon a PC board fitted in the NIM module. Shaping the outputs of the preamplifier, signals weredigitized by flash ADC CAMAC modules with 20MHz. Cosmic ray events are analyzed with the
16 pads, even if the alpha signals are difficult to be detected. Scintillation lights are read out by
500MHz FADCs for the PSD (Pulse Shape Discrimination) analysis. Performance of
purification is studied also in Xe gas phase for the quantitative evaluation.

FISCAL YEAR OF 2011

First, there was no damage by the Great Eastern Japan Earthquake, March 11, 2011, while adigital oscilloscope and a desktop personal computer fell down from the table.
In this fiscal year, following three major efforts have been conducted, that is (1) a test of the
TPC prototype with 5cm drift and 16ch pad readout, (2) strength test of a ceramic end plate and(3) development of ASIC front-end electronics.
One of major issues for the TPC prototype test is a purification of liquid xenon in the chamber.
Since the xenon gas is purified in circulating through the getter, one immediate possibility is toincrease the flow rate for efficient purification. The flow rate is limited by the cooling power ofthe pulse tube refrigerator (PTR, PDC08 of Iwatani co.). Therefore, we upgrade a helium
compressor of the PTR. Actually, the cooling power was increased from 21W to 31W at 165K,
where the flow rate can be raised from 0.4L/min to 2L/min. However, we could not keep thecooling power and we have frequently had to warm up and unfreeze the cold head of PTR for 3
months. This problem was finally solved by installation of a molecular sieve adsorption vessel atthe compressor discharge side to clean up the helium gas, September 2011. Since then, we
could operate the PTR at the flow rate of 1.4 to 1.8L/min. After the purification for 2 weeks, thecharge signal has been observed just one time, 6th October 2011. It has been a mystery why

Figure 2 : The strength test of a ceramic endplate : Left photograph shows a water leak in acircle at about 20 atm. of the water pressure. Right figure shows a ceramic plate glued on the
ICF152 SUS flange, where the water pressure is applied from right hand side. Unit is mm.

33

the observation was just one time. Finally, we found that it was due to a lower liquid level ofxenon in the chamber, February 2012. For the moment, the level must be higher about 4cm
than the TPC anode at least, where the charge (electrons) drifts upward.
We had a strength test of a ceramic endplate for next prototype with front-end electronics atthe endplate, April 2011, as shown in Fig. 2. The ceramic plate has area of 5cm x 5cm with
3.5mm thickness. The plate is glued on the SUS flange with STYCAST. It was graduallypressured by water up to 35 atm. for about 8 minutes. We observed a small water leakage at
about 20 atm. So, it shows enough strength at least at room temperature.
The ASIC front-end electronics has been developed recently in a framework of the Open-IT.
We tested a TPCFE09 chip (second version) with 16 channels/chip both at room temperature(300K) and 165K. So, it was shown to work at the liquid xenon temperature. The gain andnoise were measured to be 10-13V/pC and 1,200-1,650 electrons (ENC), respectively.

FISCAL YEAR OF 2012

In this fiscal year (2012), we have succeeded to operate the prototype TPC filled with liquid
Xe since August, 2012 until end of March, 2013. As shown in Figure 3, the TPC has 5cm drift
in the electric field of 0.5 kV/cm with a grid of 1mm gap (2.6kV/cm), where the anode consists of
16 pads in a 4x4 matrix configuration. First, charge signals are detected by pre-amplifiers
connected to each pad in the chamber followed by shaping amplifiers in room temperature.
They are digitized by the 20MHz Flash ADC (CAMAC modules). All 16 channels have been
alive and monitored by test pulses. In the chamber, two alpha sources, α1 and α2 of 241Am
are set on a wire stretched at 1cm from the anode and on the cathode plane, respectively. A
gamma-ray source of 137Cs is also installed on top of the anode (Figure 3). Twophoto-multipliers provide trigger signals from the scintillation lights. The liquid Xe of about 2.5liters was purified by circulation with the gas flow of about 1.3liters/min. The purification process
was monitored by the total charges of signals from the three sources. The total charges
rapidly increased for a month followed with saturation. For sufficient gas flow, the cold head ofpulse tube refrigerator was warmed up every morning with recovery of the cooling power by
40% for about 3 months. The total charges resumed the increase gradually followed withsaturation again. The electron lifetimes until capturing in impurities have been measured by
gammas during these purification process and the saturation states (Figure 4). Basic properties
such as the electron drift velocity and the grid transparency were also measured as a function of
applied electric fields. As shown in Figure 4, the maximum lifetime was 77 ± 7usec
corresponding to the attenuation length of 12±1cm. The oxygen equivalent concentration of
impurities was estimated to be about 6ppb, while the target value is less than 1ppb.

34

Figure 3 : TPC prototype chamber with 5cm drift. Level of liquid Xe was over 15cm of thegauge during operation in 2012. Right graph shows the growth of charge signals of thesecond alpha source α2, from 23 August to end of March 2013. profile line.

Figure 4 : Charge signals of gamma's selected by the scintillation lights during the saturation
period in 2012.12.10 through 2013.1.19 : Left shows a scatter plot of charge signals in a planeof the pulse height and the drift time. Right shows the average and RMS of the pulse heights
as a function of the drift time.
35

FPIX PROJECTKISHIMOTO, Syunji
OVERVIEWThe FPIX project has been developing a frontend circuitry for a silicon avalanche photodiode(Si-APD) array detector for time-resolved measurements using pulsed synchrotron X-rays since
FY2010. The Si-APD detector has 64 pixels in a linear array. Each pixel is 100 mm ×200 mm,
with a thickness of 10 mm. A 50-mm gap separates adjacent pixels in the array, resulting in a
total sensitive region length of 9.6 mm. The time resolution ΔT (FWHM) is expected to be 100
ps for X-rays, based on the device thickness. In order to apply the APD detector totime-resolved diffraction measurements with 2 ns pulse-pair resolving time and a count rate of
up to 108 s–1, a four-channel ASIC, 4 mm × 4 mm in size, was fabricated for processing ananosecond-width pulse from each pixel of the Si-APD in FY2010. The ASIC consists of acurrent amplifier with a baseline restorer, a comparator, and T-flip flops, as shown in the block
diagram in Fig. 1. The output signals from the ASIC are fed at a rate of 125 MHz into an FPGA
circuit.

Fig.1 Block diagram of ASIC for Si-APD array detector

In FY2011, a test board of 64-channel fast pulse electronics was developed using thefront-end ASICs fabricated in FY2010. The 64-channel Si-APD linear array was mounted on
the test board and the 64-channel X-ray detector was tested using 8-keV X-ray beam at
beamline BL-14A of Photon Factory (PF).
36

Fig.2 X-ray counting with 10-ns sampling,
recorded by channel 41of the 64-channnel
Si-APD linear array detector. Gaps of 30 ns
correspond to the empty space of the electron
bunches in the PF ringFig.3 X-ray peaks of 2-ns interval, recordedwith 1-ns sampling

Figure 2 shows a time-course X-ray counts observed by the detector. A fine 8-keV beam of 10
μm in diameter just hit one channel (ch 41) of the linear array. The detector was able to record
the four blocks of 126 ns and gaps of 30 ns between the blocks, by a 10-ns pulse-pair resolution.
The time structure of X-rays derived from the electron-bunch filling of the PF ring. In FY2012,a new circuit board for the 64-channel Si-APD linear array detector was developed for 1-ns
sampling time-resolved X-ray experiments. The circuit board consisted of the ultra-fast frontend
ASIC, a FPGA (Xilinx Spartan6), and a hardware-based TCP processor for Gigabit Ethernet(SiTCP). We tested performance of the multi-scaling measurements using the detector systemat beam line BL-14A of PF.
Figure 3 shows counts of 8-keV X-ray beam, continuously recorded with 1-ns time bin. One
can distinguish peaks with a 2-ns interval, which correspond to a part of the electron
multi-bunch structure of the PF ring. A time resolution of 1.4 ns (FWHM) was obtained in the
single-bunch part of the ring operation mode. We are now applying this detector system to thetime-resolved X-ray diffraction imaging and to the nuclear resonant scattering experiments,using both of the space resolution of 100-m and the nanosecond time resolution.

37

MEMBERS

Shunji Kishimoto, Shin-ichi Adachi, Masahiro Niwa, Shunsuke Nozawa, Hiroki Yonemura(2010-2012), (KEK IMSS)
Takaya Mitsui, Rie Haruki, (JAEA)COLLABORATORS

Shoichi Shimazaki, Masahiro Ikeno, Masatoshi Saito, Takashi Taniguchi(2010-2011), M Tanaka(IPNS)

REVIEWERS

Hirokazu Ikeda (JAXA), Youichi Murakami(KEK IMSS)PUBLICATIONS

1. S Kishimoto, H Yonemura, S Adachi, S Shimazaki, M Ikeno, M Saito, T Taniguchi and M
Tanaka, “64-Pixel linear-array Si-APD detector for X-ray time-resolved experiments”, Nucl. Instr.
and Meth. A (2013) in press.
2. S Kishimoto, H Yonemura, S Adachi, S Shimazaki, M Ikeno, M Saito, T Taniguchi and M
Tanaka, "A fast X-ray detector using silicon avalanche photodiodes of 64-pixel linear array",
Journal of Physics: Conference Series 425 (2013) 062007.
3. S. Kishimoto, S. Shimazaki, M. Ikeno, M. Saito, T. Taniguchi, and M. Tanaka, “A frontend
ASIC for a silicon avalanche photodiode linear array detector for synchrotron X-ray
experiments”, 2011 IEEE Nuclear Science Symposium Conference Record, pp. 1674-1677(2012).
4. S. Kishimoto, S. Adachi, T. Taniguchi, M. Ikeno, S. Shimazaki, M. Tanaka, T. Mitsui, “Si-APD
array detectors with 2 ns pulse-pair resolving time and sub-ns resolution for synchrotron X-ray
measurements”, Nucl. Instr. and Meth. A650, 98-100 (2011).
5. S. Kishimoto, T. Taniguchi, and M. Tanaka, “500-MHz x-ray counting with a Si-APD and afast-pulse processing system”, Proceedings of 10th Int. Conf. of Synchrotron Radiation
Instrumentation, Melbourne, Australia, September 2009, AIP Conf. Proc. 1234, 819-822 (2010).
6. S. Kishimoto, T. Taniguchi, M. Tanaka, T. Mitsui, and M. Seto, “A Si-APD array detector for
nuclear resonant scattering using synchrotron X-rays and its fast-pulse processing”,
Proceedings of the 1st international conference on Technology and Instrumentation in Particle
Physics, Tsukuba, Japan, Mar.12-17, 2009, Nucl. Instr. and Meth. A623, 608-609 (2010).

38

ASIC PROJECTTANAKA, Manobu
OVERVIEWThe ASIC project aims to increase the activity of ASIC development for sensors in the highenergy physics experiments and the experiments in the related fields.
Resources(i.e. man power and know-how) of the ASIC design are accumulated by following
processes.
1. Development of several ASICs
2. Education based on the accumulated know-how
The first step for the item 1 was supported by KEK-DTP for several years, then several
projects have developed ASICs, and we accumulated know-how of the development. The
second has been subsidized by a KEK support program for accelerator science and technology.
We’ve successfully established a collaboration network for ASIC development with experts in
JAXA, NIAS, TITec and KEK-IPNS. Until now 21 ASIC development projects, e.g. a silicon trip
detector readout ASIC, a GEM foil readout ASIC and MPPC readout ASIC, were started and theeleven of the projects(ref.1~11) were completed.
After the education program launched, we started development of QPIX in collaboration with
Tokyo Institute of Technology(TITec), Saga University, Kobe University, Nagasaki Institute ofApplied Science and KEK to perform followings.
1. Development of the higher density and sophisticated frontend electronics.
2. Development of interposer and integration technique.
3. Integration as a gas-based pixel detector.
Those developments are necessary for the next generation time projection chamber (TPC).
The basic elements used in the QPIX have been developed and the functions are confirmed.
After a graduate student left from TITec, KEK has taken over the develpment in the middle of2013. Low temperature co-fired ceramics (LTCC) as an interposer technique was evaluated andconfirmed as a promising technique for development of large area TPCs and/or a gas pixel
detectors from the view point of reliability at present. We also successfully observed heavy ion
tracks and evaluated the tracking performance.
We will continue the development effort to establish “depth and breadth” collaboration
network.
In the following sections details of the ASIC development and QPIX development aredescribed.
I ASIC DEVELOPMENT

Figure 1 shows examples of technology inheritance from the ASIC project to several
experiments. After we developed a frontend ASIC for micro pattern gas detector (MPGD) using
CMOS 0.5um for three years, in the CMOS 0.5um case all chips shown in Figure 2 are39

developed by graduate students and postdocs supervised by KEK electronics system groupbased on these know-how, so we had started ASIC development by 0.25um and 0.18um CMOS
process in parallel with educational activity(i.e. On the Job Training, seminar and training
course) for accelerator science community under limited manpower.
The figure 2 shows the number of attendee at a seminar and training courses. The number ofattendee increases year by year for the seminar and the ASIC training course. Several
universities have a plan to start up the training course by themselves at the present.

Figure 1. examples of developed ASICs and their technology transfer to other projects.

Figure 2. The number of attendee from 2008 to 201240

II QPIX DEVELOPMENT

We have been developing a gas pixel
detector as a charged particle tracking
device to accumulate design know-how ofhigher integrated and more complex readout
electronics. Each pixel has a frontend
electronics, ADC for dE/dx measurement
and TDC for Time-Of-Flight (TOF)
measurement. The QPIX measures acharged particle track by the x-y position of
the pixel and the z position by the TOF, andthe energy deposit (Q) is measured by ADC
as shown in Figure 3.
A Time-Over-Threshold (TOT) counter is
employed for dE/dx measurement in other
ASIC developments, but the TOT depends
on the particle incidence angle to the QPIX.
(e.g. TOT of a perpendicular track is smaller
than that of a parallel track to the TPC
electric field.) Therefore we employ ADC fordE/dx measurement.

Figure 3 Basic function of QPIX

There are three R&D items as follows
1. The pixel ASIC development.
2. Interposerdevelopment
forconnections between charge collection
pixel electrodes and the pixel ASIC.
3. Integration and evaluation of the three
dimensional tracking device.
The three R&D items are done by the
QPIX collaboration (Tokyo Institue ofTechnology, Saga Univ, Kobe Univ,
Nagasaki Institute of Applied Science and
KEK IPNS).
Details are described in the following
sections.

Table 1 Specifications of QPIX-v0 and
QPIX-v1

II-1 Pixel design
We have submitted two versions of QPIX-v0 and QPIX-v1 using TSMC0.18umCMOS 1P6M.

41

Those specifications are listed in Table 1. QPIX-v0 is the first prototype chip designed,

Figure 4 Block diagram of the QPIX-v1, a pixel cell and its layout

Figure 5 TOF and TOT performance in the test bench

Figure 6 SAR ADC test result (left) using the test pulse input and the result (right)
using charge collection pad
42fabricated and characterized for basic
function validation. QPIX-v0 has issues (i.e.
the number of pixel, no readout control
circuit for large amount of registers and nooffset calibration circuit in amplifiers andcomparators.).
QPIX-v1 is designed to overcome thoseissues.
Figure 4 shows the schematic of a pixel
cell in QPIX-v1 and its layout. It is composedof two main blocks: the analog block
consisting of the amplifier, the integrator, thecomparator and the SAR ADC; and thedigital block mainly consisting of the pixel
control logic, the 14-bit Time-of-Flight (TOF)
counter, the 10-bit ADC resister and the 8-bit
Time-over-Threshold (TOT) register. The
system clock of 100MHz determines thetiming resolution of TOF and TOT. The pixel
size is 200um x 200um, and the size ofactive circuit area is 130 um times 140um.

Figure 7 Intrinsic noise of the QPIX.
The red circle indicates Spectre simulation results,
and the black circle is the measurement.

The electrical measurement of a pixel in
QPIX-v1 in a test bench is shown in Figure 5
and 6.
We confirmed TOF and TOT countersmeasured the timing with 10ns accuracy.
The ADC codes show that themonotonicity can be kept; however there is
an offset of 0.6pC for the input range. The
large parasitic capacitance in the test input
line, which is totally 49pF, was connected tothe input of the transe impedance amplifier(TIA) in Figure 4. The gate timing of theintegrator in the SAR ADC is determined by
the leading edge of the TIA output. Since theleading edge timing is delayed by the43

Figure 8 Photos of charge collection pads and thebackside connected to PCB. The lower picture shows the
cross section of the LTCC structure.

additional capacitance, the ADC offset iscaused by the timing shift. Figure 6 shows
the ADC count as the function of the input
charge which is directly injected at input pad.
The offset becomes smaller than 0.6pC
shown in Figure6. The problem will besolved by adding frontend circuit in between
a pad and a current integrator.
The intrinsic noise is measured andcompared to the simulation as shown in
Figure 7. The intrinsic noise is small enoughat typical detector capacitance of 1pF.
Figure 9 The geometry measurement of bonding
surfaceII-2 Interposer development
There are several technology choices forthe interposer development. From theviewpoint of production cost and feasibility
we choose low temperature co-fired ceramic(LTCC).
Figure 8 shows the 16 layers LTCC
interposer. The interposer has 20 x 20
charge collection pads. The size of thecharge collection pad is 460um x 460um andthe pitch is 540um. The readout side has 88
solder ball whose diameter is 500um and the
Figure 10 Resistance distribution of connection for
pitch is 0.8mm. The size of the charge typical sample. The resistance value includes
collection pad on the QPIX-v1 is 70um x resistance of analog switch.
70um, and the pitch is 200um. The pad for
IO and power supply are located around the
20 x 20 charge collection pads array, and the pas size is 90um x 90um and the pitch is 150um.
The first prototype has warpage of the flip-chip bonding surface on the LTCC. It was in between
40um and 60um depends on the products. After modification of the mechanical structure, we
achieved the surface flatness less than 30um. The geometry measurement result is shown in
Figure 9. The production yield using second LTCC samples becomes 100% for 3360
connections. All samples are working. We measured resistance distribution of the connection
showed in Figure 10. The resistance variation is less than 200Ohm.
44

II-3 System integration as a charged particle tracking device
The structure of the time projection chamber (TPC) using QPIX is shown in Figure 11. The
drift space is 2.8 cm, and we use three layers of GEM for electron amplification. The HV for
GEM is 340V each. We developed another interposer for evaluation of the TPC using QPIX in
parallel with R&D of LTCC development for large area TPC. We adopted the wire-bonding
integration technology. The package is shown in Figure 11. A cover protects wire bonding andcorrects the shape of the electric field in the induction region.
Heavy ion beam at Takasaki JAEA is used for a demonstration of three dimensional tracking
and the evaluation of the TPC performance. Figure 12 shows a beam track and the resolution.

Figure 11 Cross section of the QPIX TPC and the pictures. Left bottom pictures are another
LTCC interposer with wire bonded QPIX without a metal cover and without metal cover.

Figure 12 Track of the heavy ion beam and the TPC position resolution

45

REFERENCE (FROM 2010 RELATED TO THE QPIX PROJECT)

Grant-in-Aid
1. Grant-in-Aid for Young Scientists(A) H23-26 21700k yen Kentaro Miuchi
2. Grant-in-Aid for Scientific Research(B) H21-23 14000k yen Akira Sugiyama
3. Grant-in-Aid for Exploratory Research H23-24 2,900k yen Kentaro Miuchi

Publication
1. Akira Matsuzawa, Vu Minh Khoa, Fei Li, Masaya Miyahara, Takashi Kurashina, "A newparticle detector LSI, Qpix :Integrating high speed ADC for each pixel," Nuclear Inst. andMethods in Physics Research, A623(2010), Volume 623, Issue 1, pp. 477-479, Nov. 2010.
2. “Qpix v.1: A high speed 400-pixels readout LSI with 10-bit 10 MSps pixel ADCs”, Fei Li, et al.,Nuclear Instruments and Methods in Physics Research, A650, Issue 1, pp. 101-105, Sep.
2011.
3. "NEWAGE" K. Miuchi, K. Nakamura, A. Takada, S. Iwaki, H. Kubo, T. Mizumoto, H.
Nishimura, J. Parker, T. Sawano, T. Tanimori, H. Sekiya, A. Takeda, T. Fusayasu, A.
Sugiyama and M. Tanaka Proceedings of "CYGNUS 2011 : 3rd Workshop on directional
detection of Dark Matter" Aussois, France, June 8-10, 2011 EAS publication Series 53(2012) pp. 33-41, 1109.3099 DOI:10.1051/eas/0936034
4. “A Low-Noise High-Dynamic Range Charge Sensitive Amplifier for Gas Particle Detector
Pixel Readout LSIs,” Fei Li et al., IEICE Transactions on Electronics, conditionally acceptedand expected be published in 2013.

Presentation(International conference and workshop)
1. “A new particle detector LSI Qpix: integrating high speed ADC for each pixel”
Akira MATSUZAWA (oral presentation) TIPP 2009, Tsukuba, Japan
2. “QPIX v.1:A High Speed 400-pixels Readout LSI with 10-bits 10Msps Pixel ADCs,”
Internatinal Workshop on Millimeter Wave Wireless Technology and Applications, Tokyo,
Japan, Dec. 2010
3. Fei Li, Vu Minh Khoa, Masaya Miyahara and Akira Matsuzawa, "Qpix v.1: A High Speed
400-pixels Readout LSI with 10-bit 10MSps Pixel ADCs," PIXEL2010 International Workshop,
Grindelward, Switzerland, Sep. 6 - 10, 2010
4. "R&D of QPIX", Akira Sugiyama CYGNUS 2013（oral persentaion）Toyama, Japan June 11,
2013
46

Presentation(Domestic conference and workshop)
1. "QPIX" K. Miuchi 7thMPGD workshop@Yamagata Univ. 2010/11/26
2. "QPIX" K. Nakashima 8thMPGD workshop@Kinki Univ. 2011/12/9
3. "QPIX beam test results" R. Miyashita 9thMPGD workshop@NIAS 2012/12/7
4. "Development of MPGD using a buildup method" K. Miuchi 9thMPGD
workshop@NIAS 2012/12/7
Doctor Thesis
1. “Quasi-3D Pixel Readout LSIs for Gaseous Particle Detectors”,
Fei Li 2012 Tokyo Institute of Technology
Master Thesis
2. “A pixel readout LSI with a built-in ADC for particle detector applications”
Vu Minh Khoa 2010 Tokyo Institute of Technology
3. “Development of a gas pixel detector”, Kenichi Nakashima 2011 Saga Univ.
------------------------------------------------------------------------------------------------------------------------

ref1. Development of wide range charge integration application specified integrated circuit for photo-sensor, NIMA,
vol 699, p.124-128
ref2. Development of a tracking detector system with multichannel scintillation fibers and PPD, NIMA
vol695p.206-209
ref3. A frontend ASIC for a silicon avalanche photodiode linear array detector for synchrotron X-ray experiments,
IEEE NSS CR(2012)p.1674-1677
ref4. Front-end electronics of the Belle-II drift chamber, NIMA vol735p.193-197
ref5. Development of a wide-dynamic range Front-End ASIC for W+Si calorometer,IEEE NSS CR(2012)p576-580
ref6. Development of a Time-resolved neutron imaging detector based on the uPIC micro-pixel chamber,
NIMA,vol689p.23-31
ref7.Development of an amplifier IC with wide dynamic range for Si detector in Riken Samurai spectrometer, IEEENSS CR(2012)p854-857
ref8.Development of frontend electronics for LEPS2-TPC, Keigo Mizutani, 2012 Master Thesis
ref9.ASIC design and fabrication for frontend electronics of liquid xenon TPC, TIPP09 poster presentation T.
Higashi
ref10..radiation tolerant ASIC development for muon TGC trigger system upgrade, Shuji Shichi 2011 Master Thesis
ref11. The development of time projection chamber frontend ASIC for the Neutron Lifetime Measurement, IEEENSS 2013 poster presentation H. Yokoyama

47CO2 PROJECT(TWO-PHASE CO COOLING SYSTEM)
2

SUGIMOTO, Yasuhiro
INTRODUCTION

One of the characteristics of recent detector systems for high energy physics experiments is
the high density implementation of readout electronics on the sub-detectors. Powerconsumption of these readout electronics is quite large, and efficient and low material coolingsystem is indispensable. Silicon strip sensors and silicon pixel sensors often require lowtemperature operation to reduce the dark current caused by radiation damage. The coolingsystem is an important element of detectors using these sensors, as well. For these purposes,
detector cooling systems using 2-phase CO2 as the coolant are attracting attentions recently.
Detector cooling systems using 2-phase fluid which utilizes latent heat of the fluid have beenused for several advanced detector systems such as ATLAS SCT. Because cooling systems
using 2-phase fluid utilize large latent heat, they need much less flow rate of the coolant
compared with the cooling system using water as the coolant. The heat load is consumed only
for phase transition, and the cooling with constant temperature everywhere along the coolingtube can be achieved in 2-phase cooling systems.
Two-phase coolant which has been widely used for detector cooling such as ATLAS SCT isperfluorocarbon (PFC) CnF2n+2. Compared with PFC, CO2 has much larger latent heat as shownin Table 1, and still less flow rate is necessary. Because 2-phase CO2 is used at higher pressure(1 MPa at −40°C and 5 MPa at 15°C), the evaporated vapor volume is less, and relative
pressure drop along the tube is less than PFC. Thanks to these characteristics, we can use
thinner cooling tube for CO2 than PFC, and total material budget including the cooling tube andthe coolant is less for CO2 cooling systems. Low material budget is a crucial issue to suppress
multiple scattering of charged particles and to improve the momentum resolution of thedetector.
So far, 2-phase CO2 cooling system has been successfully used for AMS tracker [1],LHCb-VELO [2], etc., which have been developed mainly by NIKHEF. Recently, R&D groups for
2-phase CO2 cooling have been started in several laboratories such as CERN, FNAL, andSLAC, mainly for the application to the LHC detector upgrade. We have started R&D of 2-phase
CO2 cooling system also in KEK. Our goal is to develop a test system of 2-phase CO2 coolingwhich can be applied for detector cooling between −40°C and near room temperature, and toaccumulate technique and know-how of the 2-phase CO2 cooling system in KEK. One big
contrast of our R&D effort to other groups is that we are aiming at developing a 2-phase CO2
cooling system using a gas compressor for CO2 circulation, while other R&D groups use liquidpumps for CO2 circulation.
48

Our group consists of members who are working on ILC TPC, ILC vertex detector, Belle-IIvertex detector, and KEK cryogenic group. The required cooling temperature ranges from
−40°C to near room temperature. However, one 2-phase CO2 cooling system can cover all thetemperature range.
CO2

C2F6

C3F8

Latent heat (at −40°C)

321 J/g~100 J/g~110 J/g

Triple point−56.4°C−97.2°C−160°C

Critical point

31.1°C

19.7°C

71.9°C

Table 1. Characteristics of coolant
BLOW SYSTEM

Before developing a circulating coolingsystem, we have constructed a so-called⑧“blow system” in which CO2 does not
Back pressure
circulate but blows off after cooling a heat
regulator
source. The schematic diagram is shown in⑤⑦
Figure 1. At the beginning, liquid CO2 froma CO2 bottle is depressurized by a needle
Heatervalve, and temperature goes down due to
Heat
Jule-Thomson effect. The temperature after⑥
exchanger
the expansion is determined by the
Dummy pressure which is set by a back-pressure
detector regulator. After cooling a dummy detector,①②
the 2-phase CO2 is used to pre-cool the③
incoming CO2 at a heat exchanger. At the④equilibrium state, the temperature drop of
the incoming CO2 is dominated by the heatCO2 bottle
Needle valve
exchange at this heat exchanger, not by the
J-T expansion (see Figure 2). The 2-phase
CO2 is completely evaporated by a heater,and exhausted to the environment throughtheback-pressure
regulator.
Phase
Figure 1. Blow system
diagram of this system is shown in Figure 2.
The state at each point of 1 – 8 in Figure 1 can be found in Figure 2. At the beginning of theoperation, the state transition of 123’4’78 occurs in Figure 2. At the equilibrium state,
the transition of 12345678 happens.
The actual system is equipped with many pressure gauges, temperature sensors, safetyvalves, and a flow meter. Photograph of the system is shown in Figure 3. With this extremely49simple system, temperature control of the dummy detector can be achieved between −40°C
and near room temperature.

Figure 2. Pressure-enthalpy (p-H) phase diagram for the 2-phase CO2 blow system

Figure 3. Photograph of the blow system
50

CIRCULATING SYSTEM

Inspired by the successful operation of the very simple blow system, we have started R&D of
a circulating cooling system using a gas compressor for circulation, which is straight extensionof the blow system. If CO2 gas which is exhausted in the blow system is compressed andcondensed to liquid again, it becomes a circulating system. Schematic diagrams of circulating
systems using a liquid pump and a gas compressor are shown in Figure 4.
Pressurecontrolsystem2-phase accumulator

Condenser
Chiller-40～20℃

CO2
Detector
Liquid pump Heat exchanger

Needle valve

CO2

Back-pressure
valveCompressor

Chiller
5～20℃

Condenser

Heater
Detector
Heat exchanger

Needle valve
Figure 4. Simplified schematic diagrams of circulating cooling systems using a liquidpump (top) and a gas compressor (bottom).
51

In the cooling system using a liquid pump, the temperature of the 2-phase CO2 is determinedby the pressure controlled by the 2-phase accumulator. Temperature of the liquid CO2 at theoutlet of the condenser is below the saturation temperature. If we want to cool the detector at−40°C, the chiller has to supply the coolant of below −40°C to the condenser. The liquid CO2transferred between the cooling plant and the detector has a temperature equal to or below thecooling temperature of the detector. Usually, a detector is located at a long distance from thecooling plant, and tight thermal insulation of the transfer tube for the liquid CO2 is necessary to
suppress the heat load.
In the cooling system using a gas compressor, on the contrary, the operating temperature of
the chiller is close to the room temperature. Liquid CO2 close to the room temperature istransferred between the plant and the detector.
Table 2 summarizes the characteristics of the cooling system using a liquid pump and a gas
compressor. Although it seems that the cooling system using a gas compressor has advantages
over the cooling system using a liquid pump, most of the high energy physics experiments using
2-phase CO2 cooling system have employed the system using a liquid pump. The main reason
is that they could not find a good oil-free compressor which can compress the gas to quite highpressure required by the CO2 system.

Table 2. Comparison of cooling systems using a liquid pump and a gas compressor
Liquid pumpGas compressor

Temp. of pump/compressor

Low (<Tdetetcor)

High

Temp. of condenser

Low (<Tdetetcor)~ Room temperatureTemp. of transfer tube:
plantdetetor

Low (<Tdetetcor)~ Room temperatureTemp. of transfer tube:
detectorplant

Low (=Tdetector)~ Room temperature(Liquid (2-phase))(Gas)

We have designed a circulating CO2 cooling system using a gas booster as the gas
compressor. The gas booster we employed is model AGD-7 of Haskel. The gas booster is an
oil-free reciprocal compressor driven by high pressure air. This air is also used for cooling of thegas booster. The maximum pressure obtained by AGD-7 is PO=7PA+PS, where PA is the driving
air pressure and PS is the suction gas pressure.
Figure 5 shows the schematic flow diagram of the system. Relatively low pressure CO2 gas iscompressed by the gas booster. The driving air is supplied by a air compressor (Anest Iwata,
52

SLP-37EEDM5) which can deliver air of 410 L/min (ANR). High pressure CO 2 gas is cooled bycooling water supplied by the chiller and liquefied at the condenser. The liquid CO2 istransferred to the heat exchanger and cooled down close to the cooling temperature. Then, CO2
is de-pressurized by the needle valve to the pressure determined by the back-pressure valve.
Liquid CO2 evaporates to some extent through the detector and the heat exchanger, and iscompletely vaporized by the heater, and goes back to the gas booster through the
back-pressure valve. In order to reduce the pulsation due to the reciprocal motion of the gas
booster, two buffer tanks and a pressure regulator is inserted in the circuit. We plan to use thissystem for cooling test of detectors between −40°C and +15°C. Parameters expected in theoperation at −40°C and +15°C are given in Table 3. For these two cases, the phase diagram isshown in Figure 6. The points numbered by 1 – 7 in Figure 6 correspond to the state at the
points numbered by 1 – 7 in Figure 5.

Table 3. Expected operation parameters of the system at −40°C and +15°C
−40°C

+15°C

Gas booster suction pressure

0.8 MPa

2.5 MPaGas booster discharge pressure

5 MPa

6.6 MPa

Driving air pressure

0.6 MPa

0.6 MPa

Liquefaction temperature at condenser

10°C

20°C

2-phase CO2 pressure

1 MPa

5.1 MPa

2-phase CO2temperature

−40°C

+15°C

CO2 flow rate

1.3 g/s

5 g/s

System volume~3.3 L

Charged CO2~750 g53

Driving air-compressor
Pa <0.8 MPa, ~400L/min
CO2

2

BufferBuffer

Back-pressure
valve

1

7
Chiller

Condenser

Gas booster

5～20℃

Heater

AGD-7
Po < 7Pa + Ps

3Regulator

Detector

4
Flow Meter

Heat exchanger
5

6

Needle valve

Figure 5. Schematic flow diagram of the circulating CO2 cooling system
Right shows the average and RMS of the pulse heights as a function of the drift time.

4

3

H

2

5

7

L

6
1

Figure 6. Pressure-enthalpy (p-H) phase diagram of the cooling cycle for the
2-phase CO2 circulating system for −40°C (L, blue line) and +15°C (H, red line)
operation.
54

The cooling system we have constructed is a system for R&D. Therefore, it is equipped withpressure gauges, temperature sensors, flow meters, and a dew point sensor at appropriate
positions. In addition, there are several valves for evacuation, ventilation, and safety. The
detailed diagram of the system is shown in Figure 7. In this figure, T, TC, P, D, DM, DI, RU, andDC stand for Pt temperature sensor, thermo couple, pressure gauge, dew-point sensor,
dew-point monitor, digital indicator, readout unit, and digital controller, respectively. Outputs of
the Pt temperature sensors are directly read out by a data logger. Outputs of other sensors areconverted to either 1~5 V or 4~20 mA signal, and read out by the data logger.
Each buffer has a volume of 1 L, which is much larger than the cylinder volume (216cm 3) ofthe gas booster. The condenser and the heat exchanger (HEX) are brazed stainless plate heatexchangers. The area of heat exchanger is 0.64 m 2 for the condenser and 0.19 m2 for the HEX.
The dew-point sensor (D) can measure the dew point down to −100°C. Usually, CO2 gas
bypasses the dew-point sensor, and occasionally the dew point is measured by switching thepath by V9. The whole system (inside the dash-dot line box in Figure 7) is housed in aaluminum frame of 1m(W)×1m(D)×1.8m(H) covered by aluminum panels for safety as shown in
Figure 8.
Assembly of the system has been completed, and we are now in the process of safety
inspection in KEK. Our system has very small cooling capacity (<3 Japanese refrigeration ton),
and is not subject to Japanese safety regulation for high pressure facilities (High Pressure Gas
Safety Act, etc.). However, KEK is keen to safety, and our system is required to satisfy theregulations.

DI2

24V

DI3

CO2

DI4

24V

AC100V

DM

RU

24V

V1
24V

Interlockcircuit

V11

F2
T

V2

24V

5～20℃

P2

RV2 24V P

V3DCAC100VRV1 Heat bath

Buffer1

TC

F3

HEX

T

F4
T
T

V5
RV3

J5

AC100V

V7

RV4

V10

GB

CV M4

T

J3

P5 P

M1

P
T

P1

Buffer2

DI1

J6

T

V4

J4
Chiller

P
24V

24V

V6
D

M2

P

T

F1

T

J2

P

V9

P P3

P6
P7 P4

24V

J1
Air
compressor

24V

DI5

24V

RV5 V8

M3
20ch

DC24V
Data
AC100V
Logger

1/4" (or glued for T)
3/8"
1/2"
Electric circuit

J8

J9

J7

Vacuum

Vent

Vent

Figure 7. Detailed diagram of the system.
55

Figure 8. Photograph of the system

SUMMARY AND PROSPECTS

We have started R&D on 2-phase CO2 cooling system at KEK for cooling of advanced
detectors for high energy physics. At the beginning of the R&D, we constructed a “blow system”
in which CO2 does not circulate. Successful operation of the simple blow system determined us
to develop a circulating CO2 cooling system using a gas compressor instead of a liquid pump.
We have designed and constructed a circulating CO2 cooling system in which a gas booster isused as the compressor. The system is about to be operated for detailed study.
The present circulating system is for demonstration of feasibility of the system using a gas
booster as the compressor. If it does not work well, we will search another possibility of the gas
compressor. One possible alternative is a compressor used for Eco-cute, a heat pump systemfor producing hot water using CO2. If the present system works well, we will develop morepractical systems, such as a system for cooling of remote detector, a more compact system,
and a remote controllable system.

REFERENCES[1] A.A.M. Delli et al., NLR-TP-2003-001 (2003).
[2] M. Van Beuzekom et al., PoS (Vertex2007) 009 (2007).
56