Development and Evaluation of a
Two-Dimensional Detector
Member:
Chiori Matsushita, Yuzuka Sasaki, Manami Sawai, Aoi Atobe, Mihiro Nukiwa

Schools:
Joshigakuin Senior High School, Osaka Prefectural Kitano High School, Kawawa
Senior High School, Junten Senior highschool, Kawagoe Girls’ High school

Team name: Sakura Particles

11. Why we want to go to CERN
We want to go to CERN to use the two-dimensional position sensitive detector wedeveloped for future use in muography. This two-dimensional detector is an innovativedetector that could be constructed for under 100,000 yen (660 US Dollars), and if put
into practical use, this detector could help lower the experimental costs. We havealready tested the detector’s one-dimensional functionality using cosmic rays andelectron beams in KEK (The High Energy Accelerator Research Organization). However,to reach our final goal, we need to test this detector using muon beams. There are nobeamlines in Japan where students can conduct experiments using muons. Thus, anopportunity to carry out an experiment at CERN is invaluable.
Also, all members of our group have experienced presentations at academic
conferences and are participating in a Japanese cosmic ray outreach group for over 150
high school students. If we were able to experiment in CERN, we would like to spread
our experience to high school students all over Japan.

2. What is a two-dimensional detector?
The detector we created can determine where a particle hits using CsI scintillatorsplaced in a 5×5 array (Fig. 1,2). The detector works in the following steps. First, when aparticle hits any of the scintillators placed in the 5×5 array, the scintillator emits light.
Next, the light reaches the four surrounding SiPM boards (Fig. 3) after attenuation
caused by air gaps when passing through the adjacent scintillators. Finally, the lightintensity ratio of each sensor to the total light intensity of the facing sensor pair iscalculated for both the vertical and horizontal axes. By using these ratios, we could
reconstruct the distribution of particle hits.

Fig. 1 Phots of developing the detector. A: Soldering the circuit board, B: Applying
light-absorbing paint to the case for light shielding, C: Performance evaluation usinga radiation source.

2Fig. 2 A 5×5 array of CSI scintillators
used in our detector. Each scintillator
measures 1cm×1cm in size.

Fig. 3 Overall picture of the detector;
it is surrounded by four SiPM boards.

3. Testing detector using cosmic rays
We began by testing our detector using cosmic rays for almost 24 hours andmeasuring background noise. For this analysis, events with extremely high or low
energy were rejected. We created two-dimensional histograms for each facing SiPM
board pair (board 1 vs. 4 and board 2 vs. 3) as depicted in Fig. 4. Five distinct lines,corresponding to five scintillators aligned along each axis, could be observed.

Fig. 4 Two-dimensional histograms for SiPM board 1 vs. 4, board 2 vs. 3, Five separatelines could be seen. Each line represents data for one row of scintillators and indicatesthe difference caused by attenuation. The result that correlation was found only in thesepairs agrees with the fact that SiPM boards 1 and 4, 2 and 3 are facing each other.

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Next, we calculated the relative locations of x and y using the following equations.

where E1, E2, E3, and E4 represent the outputs of boards 1, 2, 3, and 4, respectively.
Subsequently, the cosmic ray hit distribution was reconstructed, as shown in Fig. 5.

Fig. 5 The reconstructed cosmic ray hit distribution, The horizontal axis is x, and thevertical axis is y.
There are more events measured around the center, where stronger light wasexpected to be seen because of the placement of SiPM, but cosmic rays are detected
throughout the entire detector. From this result, we determined that our detector could
be used for imaging. Consequently, we proceeded to conduct an experiment at thebeamline in KEK for further investigation.

4. Testing detector using electron beams at KEK
Thanks to the cooperation of the outreach group we belong to, we earned anopportunity to conduct the experiment at KEK PF AR Test Beam Line (KEK-ARTBL),
where the detector’s one-dimensional functionality was tested.

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Setup for the beamline experiment
The experiment was conducted using the setting shown in Fig. 6.

Fig. 6 Setup for the beamline experiment. The irradiation positions ranged from 0 cm
(reference point) to 5 cm, at six different locations.

Experimental Method
In the experiment at KEK, a 2.01 GeV electron beam with a frequency of 1500 Hz wascollimated to a width of 1 cm with lead blocks so that it hit the detector in a vertical line.
The detector was installed on a motorized stage that could move horizontally through aremote control. Measurements were performed at six positions at 1 cm intervals, eachtaking 5 minutes.

5Analysis Procedure
As in the previous section, two-dimensional histograms were created as shown in Fig.
7. Along the x-axis, more events were measured at the points where the beam wasirradiated, while for the y-axis, the data was almost the same as the backgroundmeasurement.

Fig. 7 x-y two-dimensional histogram.
These results show that our detector exhibits one-dimensional functionality.
Consequently, we hypothesized that by conducting an experiment that changes theirradiation point along both horizontal and vertical axes, it may be possible to measure
the position of particle hits in two dimensions.

5. Proposals for experiments at CERN
Experiment Flow
As a starting point, we intend to measure the beam trajectory to establish areference detector position (Phase 1 and Phase 2) for our primary experiment (Phase 3)
Phase1: Tentative determination of beam trajectory (2 hours)
1. As depicted in Setup 1 (Fig. 8), place two Delay Wire Chambers (DWCs).
-To make the conditions the same
2. Use a muon beam with an energy of 2 GeV and a frequency of 1000 Hz.
- The reason to use a 2 GeV beam is that the previous measurements at KEK
were conducted at this energy without encountering any issues. The 1000 Hz

6beam frequency is chosen based on the maximum number of events per minutethat this detector can effectively handle.
Phase2: Measurement of the beam trajectory (5 hours)
3. As illustrated in Setup 2 (Fig. 8), place black cloth to block out light.
-The black cloth will be used in subsequent experiments, so it is placed at thisphase to maintain consistent conditions. Stage for detector movement is installedinside the black cloth. It can be remotely controlled to adjust the detector’sposition.
4. Emit a beam.
5. Record the detailed beam position.
-This information will serve as a reference to place the detector in the next
experiment.
Phase3: Test the two-dimensional position sensitive detector (7 hours)
6. Direct the beam to the center of the 25 scintillators under the same conditions as
the previous experiment and conduct measurements for all 25 positions.
7. Repeat the measurements in the reverse order for all 25 positions.
-This step is to consider the potential effect of cloth radioactivation on themeasurements.

Fig. 8 Setup 1 and Setup 2: The configurations planned for use in the experiments atCERN.

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-Proposed ScheduleWe conduct our experiments in the following vein.
day

１Phase1〇

Phase2Phase3２３４５６〇〇〇〇

７８９〇〇〇〇

backupday

Experimental Equipment
1. Equipment to bring.
-A stage to control the detector’s movement-A two-dimensional position sensitive detector and its cable to operate it
2. Equipment to borrow.
-Two Delay Wire Chambers (DWCs)-A table with a length of more than 2.5 m that can be moved both up and down
freely6. Outreach activitiesFor us high school students, the opportunity to conduct experiments at CERN andDESY is precious. Thus, we will disseminate our BL4S experience in many ways. We are
all participating in Accel Kitchen LLC, Japan’s largest particle physics outreachcommunity, which supports more than 150 high school students from all over Japan andother countries. This community offers multiple platforms and events that facilitate
both offline and online interactions among students. Through reporting our experiments
in BL4S, we can inspire more students in our community to be interested in BL4S (Fig.
8).
Furthermore, Accel Kitchen LLC actively communicates our research activities toexternal students and researchers through conferences, social media, and outreach
events BL4S (Fig. 9,10). This allows us to share our BL4S experience, encouraging awider range of students to be interested in accelerator facilities. We believe thesecontributions will lead to the growth and development of the high school student
scientific community.

8Fig. 8 In March 2024, this research plan was introduced during a workshop aimed atJapanese junior high and high school students

Fig. 9 In October 2023, We showcased and introduced the detectors we have developed
at our booth exhibition at the Science Fair held in Tokyo.

7. Acknowledgement
The work is supported by the KEK PF AR
Test Beam Line (KEK-ARTBL), withspecial thanks to Dr. Yoichi Ikegami andDr. Isamu Nakamura. We would like tothank all the people involved in Accel
Kitchen, LLC who performed theexperimental operations at KEK-ARTBL
on our behalf.

Fig. 10 The members are activelyengaged in particle physics awarenessactivities through social media, one of us
achieving over 1 million impressions on X.

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