Ⅱ-8. Accelerator

RIKEN Accel. Prog. Rep. 48 (2015)

Beam Energy and Longitudinal Beam Profile Measurement Systemat the RIBF†
T. Watanabe,∗1 M. Fujimaki,∗1 N. Fukunishi,∗1 H. Imao,∗1 O. Kamigaito,∗1 M. Kase,∗1 M. Komiyama,∗1N. Sakamoto,∗1 K. Suda,∗1 M. Wakasugi,∗1 and K. Yamada∗1Upstream C20

Downstream C22Fig. 1. Longitudinal profiles the 19 F9+ beam measured atC20 (upstream) and C22 (downstream) in the AVF cyclotron beam transport line as displayed on the graphical user interface.
†∗1Condensed from the proceedings in 5th International Particle Accelerator Conference (IPAC’14)
RIKEN Nishina Center

C20 : Fitted by Gaussian function
C22 : Fitted by Gaussian function

12000

Center TC22 :6.95 ns

10000

TDC Yield (counts)

Monitors with plastic scintillators as sensors (scintillation monitors) were fabricated to measure the energy and longitudinal proﬁles of heavy-ion beams at
the RIKEN RI beam factory (RIBF). Six pairs of two
scintillation monitors installed in the transport lines
were used to measure the particle time-of-ﬂight (TOF)
between the paired monitors to determine the acceleration energy of the heavy-ion beams. The energy ofthe beam can be calculated from the measured TOF.
In addition, ﬁve scintillation monitors were installed
to measure the longitudinal proﬁles of the heavy-ionbeams. Longitudinal beam proﬁles were obtained byusing a time-to-digital converter (TDC), which digitizes the detected signals from the scintillator and theRF clock signal. Recently, to help users operate thesystem more easily, a new embedded processor witha higher-performance CPU has been introduced, anda new user interface has been constructed using theLabVIEW program.
For data acquisition and control of the scintillation
monitors, we developed a ccompactPCI system thatuses a Windows-based PC1) . Signals from the detectors are ampliﬁed and converted to logic pulses by
a constant-fraction discriminator. The TDC digitizes
this pulse along with the RF clock and stores the events
into the memory of the TDC. The TDC (TC890) has
two memory banks based on a so-called ping-pongmemory architecture that enables data readout while
the module continues to acquire events. When a bankis ready to be read, an interrupt is generated, andthe readout starts in the direct memory access mode.

Center TC20 :13.00 ns

C22C208000
6000(1-V):
7.23 deg.

4000(1-V):
6.67 deg.

2000
00510

1520

Time (ns)Fig. 2. Gaussian functions fit to the rightmost beam profiles at C20 and C22 in Fig. 1.

The programs for the data acquisition, control, and forshowing results are written in LabVIEW (Windows7).
The PCs are connected to a laptop in the main control room located 100 m from the Riken ring cyclotron(RRC) hall via Ethernet and remote desktop connection. The EPICS system controls insertion of the monitor into the beam line or its retraction from the beamline and it monitors these statuses.
We measured the energy of a 19 F9+ beam accelerated by the AVF cyclotron by using the TOF method.
The 19 F7+ beam was used to produce element 105,
262
Db from a target of 248 Cm2) . Because the sequential double pulse resolution was 15 ns, the 19 F9+ beam
was attenuated to be under 1 M s−1 using beam attenuators. The longitudinal proﬁle of the 19 F9+ beam wasmeasured at C20 (upstream) and C22 (downstream) in
the AVF cyclotron beam transport line were displayedon the graphical user interface as shown in Fig. 1. The
rightmost longitudinal proﬁles obtained at C20 andC22 in Fig. 1 are expanded and plotted in Fig. 2. By
ﬁtting the proﬁles in Fig. 2 with Gaussian functions, we
determined the center times TC20 and TC22 of the proﬁles and the longitudinal phase widths (1-σ), as shownin Fig. 2. The beam kinetic energy (TT OF ) obtainedby measuring the TOF was 6.81 MeV/u. In addition,
the beam kinetic energy (TBρ ) can be determined by
the magnetic ﬁeld of the bending magnet that bends
the 19 F9+ beam because the ﬁeld was already known
as a function of the exciting current. In this measurement, the hysteresis eﬀect was not taken into account.
The kinematic energy TBρ was determined to be 6.80
MeV/u. These energies are in good agreement, with adiﬀerence between TT OF and TBρ of 0.1%.
References
1) T. Watanabe et al.: RIKEN Accel. Rep. 43, 135 (2010).
2) M. Murakami et al.: RIKEN Accel. Rep. 47, 265 (2014).

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