RIKEN Accel. Prog. Rep. 50 (2017)

Ⅱ-8. Accelerator

Beam energy measurement system using
electrostatic pickups at the RIBF
T. Watanabe,∗1 N. Fukunishi,∗1 M. Fujimaki,∗1 and R. Koyama∗2
It is important to measure the beam energy of heavyion beams at the RIBF. Monitors with plastic scintillators as sensors (scintillation monitors) were used tomeasure the energy and longitudinal proﬁles of heavyion beams.1) However, the beam cannot be used while
it is being measured, and there is a danger of melting
the scintillator. For the purpose of real-time measurement of the beam energy, electrostatic pickups were
newly designed, fabricated, and installed in the beamtransport line (C01, C02) in the AVF cyclotron.2) Twoelectrostatic pickup monitors installed in the beamtransport line are used to measure the particle time- ofﬂight (TOF) between the paired monitors. Researchers
who conduct experiments can always watch the beamenergy in real time with a web browser even if they are
in an experiment room.
When a charged-particle beam passed along the axisof the electrostatic pickup, the image charge is electrostatically induced on the pickup. The beam signals
are ampliﬁed and transmitted via coaxial cables witha length of 46 m directly to the DAQ stage outside theradiation protected area. Finally, a high-speed digitizer board digitizes the beam signals and sends thedate to a controller PC. We chose this digitizer for thesignal processing instead of a standard oscilloscope because it has high transfer rates and large-capacity onboard memory.
The electrical speciﬁcations of thedigitizer and ampliﬁer are listed in Table 1. The program for the data acquisition of the digitizer and for
displaying results is written in LabVIEW. Since thecontroller PC in the DAQ stage is connected to an
EPICS Ethernet LAN, the measured results can bewatched with a web browser on any PC, only users
have permissions. The obtained data are stored in a
Table 1. Electrical speciﬁcations of digitizer and ampliﬁer.
Digitizer
Model No.
Bandwidth
Sampling rates
MemoryResolution
Channels
Transfer Rates
Ampliﬁer
Model No.
Bandwidth
Noise FigureGain∗1∗2NI PXIe-5160 (National Instruments)
DC - 500 MHz
2.5 GS/s (1 ch), 1.25 GS/s (4 ch)
2GB10-bit
4600 MB/s

Beam signals
C010.2V
10 ns

10 minC02

Short term record
5x10-48x10-4
1 hourLong term record

Fig. 1. Example of the measured results for the acceleration of a 2 H+ beam at an intensity of 10 μA.

MyDAC, which is a simple data-logging and display
server. An example of the measured results for theacceleration of a 2 H+ (deuteron) beam with an intensity of 10 μA is shown in Fig. 1. In these results,
the beam energy was found to be changed periodically with a period of about 6 min. This phenomenon
was synchronized with a temperature change of cooling water, which was caused by a heat exchanger andtemperature-control device. The temperature of cooling water was changed within ±0.4◦ C every 6 min.
Although the investigation indicated that the beamenergy change might have been caused by the temperature change of the main coil of the cyclotron, moredetailed investigation is necessary. The accuracy canreach better than 0.2% for the energy spread assuming
precisions of the length ΔL = 1 mm and time Δt =100 ps. The minimum detectable beam current withthis system is approximately 50 nA.
In ﬁscal year 2016, we measured the beam energy
12 times for the cross section measurements for RI
production experiments,3–7) which typically lasted for
3 days. Those beam-energy measurements were performed using the scintillation monitors and electrostatic pickup monitors.
References
1) T. Watanabe et al.; Proc. IPAC’14 (2014), p. 3566.
2) T. Watanabe et al.; Proc. 12th Ann. Meet. of PASJ,(2015), p. 1198.
3) S. Takács et al., NIM B 383, 213 (2016).
4) F. Ditrói et al., NIM B 385, 1 (2016).
5) S. Takács et al., NIM B 397, 33 (2017).
6) A. Usman et al. NIM B 399, 34 (2017).
7) A. Saito et al., ARI 125, 23 (2017).

ABL0300-00-3230 (Dynamic RF Inc.)
9 kHz - 3.0 GHz
2.5dB typical, 3.0 dB Max @25 ◦ C
32 dB @25 ◦ C

RIKEN Nishina Center
SHI Accelerator Service Ltd.

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