DEVELOPMENT OF PEPPER-POT EMITTANCE MONITOR FOR
HIGH-INTENSITY ION BEAM ACCELERATED BY RIKEN AVF CYCLOTRON

Yasuteru Kotaka, Keita Kamakura, Hidetoshi Yamaguchi, Nobuaki Imai, Yasuhiro Sakemi, Center for Nuclear Study of the University of Tokyo (CNS)
Jyun-ichi Ohnishi, RIKEN Nishina center,
Kichiji Hatanaka †, RCNP, Osaka University

At the Center for Nuclear Study of the University of Tokyo (CNS), the measurement of Electric Dipole Moment (EDM) of Francium (Fr) isunderway with the world highest precision. Fr is generated by nuclear fusion reaction by irradiating the gold (Au) target of EDM
experiment device (EDM target) with oxygen ion beam 18O6+ of 7 MeV/u accelerated by RIKEN AVF Cyclotron.

Our goal is transporting beam of more than 18 eµA (400 W), without loss and converging beam to be 1 mm of SD ofbeam distribution on the EDM target.
AVF Cyclotron and beam transport system to C12,CRIB, and E7B

Pepper-pot emittance monitor
PEM mask

Our problem
Beam transport efficiency is average 66 %When beam intensity > 10 eµA
Beam emittance expands as intensity increase

Glowing at the positions
Cupper plate
where beams hit
Diameter of hall 0.3 mm
Distance between holls 2mm
Thickness 1 mm
tilted 45 degree

beam

Old emittance monitor (EM_C01) cannot measure High intensity beam because Cooling Ability < 130 W beam.
has unsolved measurement error.
①reducing the radiation damage to a camera
Developing Pepper-pot emittance monitor for high intensity beam
②required angular accuracy for the accelerated beam
We need more three additional development.
③beam shutter system to avoid heating PEM due to beam

① reducing the radiation damage to a camera - tele lens optics of camra Achieving 2200 mm between Camera and PEM by nowperiscope

Tele lens only

Add intermediate lensPEM

Achromatic lens The view of fluorescent plate
After using Achromatic lens
focal length
200mm
Original image After processing

The relationship between position andthe difference made by the distortion of
the tele-lens method

CameraNTSC 720 x 480

SD 0.16mm②required angular accuracy for the accelerated beam
The way estimating σ matrix assumed to be true
Schematic view of C03 beam line

Equation of σ matrix. σ11 known

estimate the beam size including error at the EDM target
due to the EM_C01 measurement error.
random numbers following
Error simulation
4-variables normal distribution
Calculated phase space at z=0

19F7+ 6.68MeV/u 5eµA

xSD 7.1mm→ notsolved

ySolution of equation(SDx of PF_EM 8 mm)
Z=0Measured beam profile by PF_C02
xySD5.6mm

SD4.8mm

Measured beam profile by PF_C03
xsimilar
SDySD
1.6mm

2:1:

Measured beam profile by PF_EMSD2.8mm

SD 0.14mm

C12EDM Target
𝝈 matrix assumed to be true
At EM_C01xydp/p=0.006③Beam shutter system to avoid heating PEM from beam
No cooling － to shorten the measurement time
The beam stops by applying a high voltage to the electrode set in thebeam line just behind an ion source and bending the beam sideways.
The measuring time reachs 0.27 seconds-2kV, rising time 0.15 sec
HV ONBendingbeam

𝝈 matrix assumed to be true
To EDM Target (TRANSPORT）

The relationship between angularerror of EM_C01 and calcurated
beam size (SD) at EDM Target

PF_C03 calculated using above 𝝈 matrix1.3mm

The diagram of the beam shutter control system

1:adding random numbers following
normal distribution having SD as error
2: Recomputing angle

HV OFFGostraight

Required less than0.3mradof angular accuracy of PEM

Dividing the measurement errors of PEM from theemittance assumed to be true by error simulation.

Our requirement for facility of beam test
・low beam emittance,・no correlation between x and y,・three BPMs in a beam line,
Micro Analysis Laboratory, Tandem accelerator (MALT), The
University of Tokyo. The PEM installation with tele lenscamera optics was complete. This beamline has two BPMs
at 735 mm upstream and 2070 mm downstream from thePEM. Moreover, since the PEM becomes BPM with theaverage position error of 0.15 mm, we have three BPMs.