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BEAM PROFILE MEASUREMENT USING HELIUM GAS LIGHT
EMISSION AND BEPM FOR SUPERHEAVYELEMENT SEARCH EXPERIMENT
T. Watanabe∗ , T. Adachi, P. Brionnet, O. Kamigaito,K. Morimoto, T. Nishi, A. Uchiyama, RIKEN, Wako, Japan
A. Kamoshida, National Instruments Japan Corporation, Tokyo, JapanK. Kaneko, R. Koyama, SHI Accelerator Service Ltd., Wako, JapanThe newly constructed superconducting linear accelerator(SRILAC) is now in operation with the aim of discovering
new superheavy elements and advancing the production of
medical radiation isotopes. Because it is crucial to extend thedurability of the expensive Cm target for as long as possible,
these experiments require the accelerated V beam to be
sufficiently widened. To this end, a helium gas light emission
monitor (HeLM) has been introduced to measure the beamprofile. Because He gas flows within the target chamber,by capturing the light emitted from He gas with a CCD
camera, the beam profile can be obtained nondestructively
and continuously. These measurements are handled throughprogramming in LabVIEW, with analyzed data integrated
into an EPICS control system. A method to estimate thebeam envelope has been recently developed by leveraging themeasured quadrupole moments with beam energy position
monitors (BEPMs), and incorporating calculations of thetransfer matrix. The synergistic use of HeLM and BEPM
plays a useful role in accurately controlling the beam size at
the Cm target.

INTRODUCTION
To upgrade the RIKEN Heavy-ion Linac (RILAC), the Superconducting RILAC (SRILAC) has been constructed, andsuccessful commissioning has been completed [1]. Theseaccelerators are being operated to advance research intoeven heavier synthetic elements [2]; build on the discoveryof element 113, Nihonium [3]; and enhance the production
capability of the short-lived radioisotope 211 At, which isanticipated to have applications in cancer therapy [4]. Overthe past three years, the V beam, accelerated by both theRILAC and SRILAC, has been irradiated onto the Cm target
for superheavy elements research.

BEAM PROFILE MEASUREMENT USINGHe GAS LIGHT EMISSION

prevent the Cm targets from melting due to the beam irradiation, several thin Cm targets are mounted on a 30-cm radiuswheel, which rotates at 2000 rpm. GARIS III separates thesuperheavy elements from the unwanted particles, achieving high background noise reduction, by using dipole andquadrupole magnets. Furthermore, helium gas is introduced
so that the electron charges of the superheavy elements converge to a certain value. Even if superheavy elements withdifferent charges are ejected from the target, because thecharges of superheavy elements become equal while they
are passing through the helium gas, it is possible to collectthe desired superheavy elements.

Target Chamber and HeLM for GARIS III
To protect the Cm target, it is essential to extend its durability for as long as possible. Therefore, the accelerated V
beam must not only hit the Cm target but also be adequately
widened. A schematic drawing of the beam line with a differential pumping system and the target chamber for GARIS
III is shown in Fig. 2. Baffle electrodes are installed at thetop, bottom, left, and right to detect the edge of the beam,
and a carbon slit is installed in front of the target to cut theedge of the beam. CCD cameras monitor how the beamirradiates the target through view ports located upstream
and downstream of the target. In Fig. 2, the beam comesfrom the left side, hits the Cm targets, and then proceeds toGARIS III. Since He gas flows within the target chamber,
To RRC(Future plan)∗ wtamaki@riken.jp

Beam

Target chamber
He gas light monitor (HeLM)
Production apparatus
for medical RIs

RILAC, SRILAC, and GARIS IIIA schematic drawing of the RILAC, SRILAC, GARIS III,and production apparatus for medical RIs is shown in Fig. 1.
The V beam, accelerated by both RILAC and SRILAC, isirradiated onto the Cm targets inside a target chamber. ToSRILAC

FromRILAC

e00
Beam

Abstract

GARIS III

Figure 1: Schematic drawing of the RILAC, SRILAC,GARIS III, and production apparatus for medical RIs.
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12th Int. Beam Instrum. Conf.
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12th Int. Beam Instrum. Conf.
ISBN: 9 7 8 - 3 - 9 5 4 5 0 - 2 3 6 - 3

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d o i : 1 0 . 1 8 4 2 9 / J A C o W - I B I C 2 0 2 3 - W E P 0 0 7HeLM

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Differential pumping system

Target chamber

CCD Camera Mirror

Table 1: Specifications of the Lens, CCD Camera, and Video
ServerTarget wheel
TMP

TMP

View port
N2-gas-jet curtain

View port
PIN diode

N2FromSRILAC

TMP

TMP
BaffleelectrodesTMP

MBP

MBP
Ta and C Slit

MotorToGARIS III

Faraday cup

1485 mmFigure 2: Schematic drawing of the beam line with the differential pumping system and target chamber for GARIS III.
its electrons are excited through collisions with the beam,and the light is emitted when the electrons return to their
ground state during the de-excitation process. By capturing
the emitted light with a CCD camera, the beam profile canbe obtained nondestructively and continuously.
A picture of the target chamber and the He gas light monitor is shown in Fig. 3. Hereafter, the He gas light monitor
is referred to as “HeLM”. To detect the light emitted fromhelium gas, a light window is located at the top of the targetchamber. Since the target chamber is in an extremely highradiation environment, the light-receiving elements for theCCD camera gradually deteriorate as the experiment progresses. The CCD camera used for the HeLM is a small
commercial monitor camera that employs CMOS elements.
To minimize deterioration, the emitted light is reflected by amirror located near the light window, and the reflected lightis received by the CCD camera, which is set far from thetarget. However, even with this system, radiation damage
cannot be completely avoided, and the CCD camera needs
to be replaced approximately every two months. The detachable lens is reused after the CCD camera is replaced.
The image signal obtained with the CCD camera is sent to avideo server through an analog cable, and the digitized image data are transmitted to a HeLM controller via Ethernet.
The specifications of the lens, CCD camera and video server
are provided in Table 1.

Mirror

CCD camera

Targetchamber

Figure 3: Photograph of the target chamber and HeLM.
The emitted light is reflected by a mirror located near thelight window and the reflected light is received by the CCDcamera.

CCTV∗ LensFocus
IrisSensor
Video resolution
Electrical shutter
Model No.
Chanel number
Video compression
Resolution
Frame rate
Processor
MemoryCCTV∗

Lens for CCD camera
For 1/3 or 1/4 inch sensor
Focal length 6-60 mm (variable)
Manual F1.6
CCD camera
Sony307 1/3 inch CMOS
Pal/NTSC 1920 × 1080
1/50 ∼1/10,000 s
Video server
AXIS Q7404
4H.264�MPEG-4 Part 10/AVC�
Motion JPEG
720 × 480 ∼176 × 120
30 frames/s
ARTPEC-3 × 4
Main 128MB × 4,
Flash 128MB × 4
Closed Circuit Television

Programming for Image Acquisition and Analysis
with LabVIEW and Web API
To analyze the beam profile, the HeLM controller obtains
image data from the video server using a Web API (Application Programming Interface). The program to access thevideo server and save the acquired data is implemented withthe Web API and the C++ OpenCV library. To achieve nearreal-time performance, one image frame is acquired every
200 ms.
The image data acquisition and analysis program is built
using LabVIEW. LabVIEW includes a “Vision Development Module” designed for developing image processing
applications to automate visual inspection tasks in industrial
and other fields. This module contains “NI Vision Assistant” software, which allows developers to create application
software interactively, confirming the results step by step.
After confirming that the application software was working
correctly, it was converted to a VI (Virtual Instrument) andintegrated into the main HeLM program. The program could
be completed in a short period of time using the NI Vision
Assistant.
The front panels of the aforementioned application software and the analyzed results of the emitted He gas light are
shown in Fig. 4. Since the details of the target are confidential, the length is expressed in pixel dimensions. The upperand lower front panels can be switched using a tab selectionbutton. In the upper front panel, the measured results andsetting selections are displayed as follows: (a) The result ofintegrating the brightness in the direction of travel of thebeam and the result of a Gaussian fit, (b) An image of Hegas emission, (c) The value of a Gaussian fit 1𝜎 and thedeviation from the center, and (d) The setting panel for theWEP007
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03 Transverse Profile and Emittance Monitors

12th Int. Beam Instrum. Conf.
ISBN: 9 7 8 - 3 - 9 5 4 5 0 - 2 3 6 - 3fitting region, which can be selected manually or throughdirect numerical input.
The result of the integrated luminance along the beam
direction represents the transverse beam profile, and theGaussian fitted 1𝜎 is defined as the beam width. In the lower
panel, the history of the Gaussian fitted 1𝜎 is recorded at
the following scales: 1 minute (top), 1 hour (middle), and 1day (bottom), as shown in Fig. 4(e). If the experimental user
sets the maximum and minimum thresholds for the beamwidth 1𝜎, and the beam width exceeds those thresholds, theHeLM controller can automatically send a warning email tothe user.
At the RI Beam Factory (RIBF) at the Nishina Center
for Accelerator-Based Science, the distributed control en-(a)(c)

IntegratedBeam(b)
(d)

(e)

vironment system known as EPICS (Experimental Physics
and Industrial Control System) has been implemented tooperate and manage accelerators and large-scale experimental apparatuses. EPICS facilitates communication between
servers and clients using the communication protocol known
as Channel Access (CA). Here, the Input Output Controller(IOC) is a pivotal software component within EPICS thatconnects the controlled devices to the CA communication
network and offers so-called Process Variable (PV) data.
The analyzed data obtained by the HeLM monitor are stored
in the PVs. However, due to security considerations, theHeLM controller is linked to the general LAN, which is isolated from the dedicated EPICS LAN. Consequently, datafrom both networks are relayed through a proxy server using
the HTTP client method.

MEASURED BEAM WIDTH WITH
HeLM AND BEAM OPTICSCALCULATIONS USING BEPM
We discuss the HeLM measurements and beam optics
calculations by using an example of accelerator operations
conducted on 29 June 2022. In the early morning of thatday, the experimental user requested that the beam optics bereadjusted because the beam width measured using HeLM
had decreased from 37 pixels (before the adjustment) to 31
pixels. While we attempted to adequately widen the beam on
the target, the beam loss needed to be minimized as much aspossible. To this end, we calculated the beam optics and adjusted them using the calculated results. Figure 5 shows theelastic scattering measurement results (red line), the beamwidth measured by the HeLM (blue line), and the carbon slit
current (green line). After the beam optics were adjusted
from 10:34 to 11:00, the beam width was improved from31 to 37 pixels, as shown by the blue line in Fig. 5. The
beam transmission efficiency, defined as the ratio of the up2022/06/29

1 Minute
1 Hour
1 Day
Figure 4: The front panels programmed with LabVIEW. (a)Result of integrating the brightness in the direction of travelof the beam and the result of a Gaussian fit, (b) Image of Hegas emission, (c) Value of a Gaussian fit 1𝜎 and the deviationfrom the center, (d) Setting panel for the fitting region, and(e) Record of the Gaussian fit 1𝜎.

Adjustment
process

Adjustment
process

Figure 5: Measured results of elastic scattering (red line),beam width measured by the HeLM (blue line), and carbon
slit current (green line).
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12th Int. Beam Instrum. Conf.
ISBN: 9 7 8 - 3 - 9 5 4 5 0 - 2 3 6 - 3
QD

QF Q D

Dipolemagnete00

X-max. 0.3 m

30 mm

X-direction

30 mm

Y-direction

1.000 m0m

10.9 mFigure 6: Calculated result of the beam envelope from e00
to the target chamber.
stream beam current to the target one, decreased from 97%
to 94%. As shown in Fig. 5, the elastic scattering (red line)
and the current of the carbon slit installed just in front of
the target (green line) also obviously decreased. The beam
current from the carbon slit has a characteristic in which thecurrent increases rapidly just after beam irradiation and thengradually decreases. Therefore, the HeLM, carbon slit current, and elastic scattering measurements are in qualitativeagreement.
The calculated results of the beam optics from e00 (seeFig. 1) to the target chamber [5] are shown in Fig. 6. Here,the emittance and Twiss parameters are obtained by the Qscan method by using a wire scanner installed upstream ofSRILAC, and the transfer matrix is calculated from thesevalues to provide optimum conditions at the target. The beam
is focused just before the target to increase the spot width,
and the beam width measured by the HeLM is fine-tuned tooptimize the quadrupole magnet.

1412Beam Width (arb.)

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QF

Target chamber

QD QF QD

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Normalize by values at 94A
10864(a) BEPM + Optical calculation(b) View port(c) He gas light monitor

2088

90

92

94

96

98

100102

Excitation Current of Quadupole Magnet QD0A1a (A)Figure 7: The beam widths obtained by: (a) the beam optical
calculation using the quadrupole moments measured by theBEPMs, (b) the target spot on the fluorescent target observed
through the view port, and (c) the measurement result takenwith the HeLM.

Furthermore, we examined the beam width measurements
and the beam optics calculation using the BEPMs [6] bychanging the excitation current of the quadrupole magnet
located in front of the target chamber. Figure 7 shows thebeam widths obtained by (a) the beam optical calculation
using the quadrupole moments measured by the BEPMs, (b)the target spot on the fluorescent target observed throughthe view port, and (c) the measurement result taken withthe HeLM. Since these beam widths have different scales,
they are all normalized to the excitation current of 94 A.
The beam widths analyzed by these methods are in goodagreement.

CONCLUSION

In the superheavy element search experiment, the beamprofile is obtained with a CCD camera by observing thelight emitted when the beam passes through the helium gas
in the target chamber. This method has the advantage thatthe beam profile can be obtained nondestructively and continuously. These measurements are handled through programming in LabVIEW and the analyzed data are integrated
into an EPICS control system. Furthermore, a method toestimate the beam envelope has been recently developed byleveraging the measured quadrupole moments with BEPMs,
and incorporating calculations of the transfer matrix. The
synergistic use of HeLM and BEPM allows us to accurately
control the beam size at the Cm target.

ACKNOWLEDGEMENTS
The authors would like to thank Dr. Hiromitsu Haba
and Dr. Daiya Kaji for providing detailed information on
the superheavy element search experiment, and Dr. Yutaka
Watanabe for supplying the CAD data.

REFERENCES[1] K. Yamada et al., “Successful Beam Commissioning ofHeavy-Ion Superconducting Linac at RIKEN”, in Proc.
SRF’21, East Lansing, MI, USA, Jun.-Jul. 2021, pp. 167.
doi:10.18429/JACoW-SRF2021-MOOFAV01[2] H. Sakai et al., “Facility upgrade for superheavy-element
research at RIKEN”, Eur. Phys. J. A, vol. 58, 2022, pp. 1–15.
doi:10.1140/epja/s10050-022-00888-3[3] K. Morita et al., “New Result in the Production and Decay of
an Isotope, 278 113, of the 113th Element”, J. Phys. Soc. Jpn.,
vol. 81, p. 103201, 2012. doi:10.1143/JPSJ.81.103201[4] H. Haba et al., “Present status of 211 At production at
the RIKEN AVF cyclotron”, RIKEN Accel. Prog. Rep.,
vol. 53, 2019, p. 192. https://www.nishina.riken.jp/researcher/APR/APR053/pdf/192.pdf[5] T. Nishi et al., “Emittance Measurement and Ion Optics
Tuning for SRILAC Beamline”, in Proc. of the 17th Annual
Meeting of Particle Accelerator Society of Japan, Sept. 2020,pp. 116–119. https://www.pasj.jp/web_publish/pasj2020/proceedings/PDF/THOO/THOO08.pdf[6] T. Watanabe et al., “Commissioning of the Beam Energy Position Monitor System for the Superconducting RIKEN Heavyion Linac”, in Proc. IBIC’20, Santos, Brazil, Sep. 2020,
pp. 295–302. doi:10.18429/JACoW-IBIC2020-FRAO04

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