Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 50 (2017)

F ast beam interlock system at BigRIPS separator
K. Yoshida,1 Y. Yanagisawa,1 K. Kusaka,1 K. Tanaka,1 and T. Kubo1,2A fast beam interlock system (FBIS) with a response timeless than 1 ms has been developed and installed at BigRIPS
in order to cope with the recent increase of beam intensity
at RIBF. If an intensive beam such as 238U and 48Ca beams
with an energy of 345 MeV/nucleon and intensity of 1
particle μA was mis-steered and incident on the beam ductowing to a failure of magnet power supplies, the duct will
be melted within 1- 5 ms. The fast interlock system detects
the failure and cuts off the beam within 1 ms to prevent
severe damage.
The FBIS at BigRIPS utilizes a compact RIO system(cRIO) of National Instrument Co. Ltd to achieve a fast
response and flex configuration capability. A prototype ofthe system was developed in 2013 and tested.1) Based on
the successful test results,1) the FBIS was constructed tomonitor the analog and digital signals from the production
target system and power supplies of the 34 magnets placedat the primary beam line and BigRIPS where a high-power
primary beam is transported. The system consists of 5cRIOs (three cRIO-9075 and two cRIO-9068) and sends thebeam stop signal to the beam chopper system as well as thenormal beam interlock system (BIS).2) NI-9222 ADC
modules and NI-9401 digital I/O modules are used foranalog and logical signal processing respectively.
Figure 1 shows the logic diagram of the FBIS. The
diagram is almost same as that for the prototype system but
two enhancements were made. A digital filtering algorithm
was added to analog signal processing in order to eliminate
the noise in analog inputs. The moving average method wasemployed as the filtering algorithm. Another improvement
was in the pulse rate measurement. A periodic counter wasformed in the control logic and logical signal pulses werecounted. The counter had a special function to produce anerror signal immediately when the counting number
exceeded the limit. Thus, one can set a rate limit to logicalsignal pulses unless waiting for the counting to end. All
these control logics were stored in a field-programmablegate array (FPGA) of the cRIO-9075 and cRIO-9068

modules and executed at fast speed.
The control conditions such as limit values of analog
inputs and pulse rates, enable/disable flags, andpositive/negative logic selections are dynamically set fromthe comprehensive control system of BigRIPS.3) The status
of faults and digitized values of the analog inputs aremonitored and logged by the control system of BigRIPS.
In the operation of the FBIS, current monitor outputs andfault signals of magnet power supplies are connected to theanalog and logical signal inputs, respectively. The
temperature monitor and rotating speed signals of theBigRIPS rotating target system4) are also connected to theanalog input of the FBIS. Interlock windows of analog
signals are set to +0.3% for dipole magnets and +1.5% for
quadrupole magnets. Windows of +15% are set for therotation speeds of the rotating targets and an upper limit of700  is set for the target temperature.
The response time of the FBIS was measured using
beams at RIBF. A logical test signal was applied as thelogical input of the FBIS. Signals from the beam trigger
counter, which measures the secondary beam produced
from the accelerated beam at the third focus (F3) of theBigRIPS separator, was monitored to determine the beam
stopping timing. Measurements were performed for 48Ca
and 238U primary beams, and in both cases, time differencesfrom the test signal input to the disappearance of the beam
trigger signal were about 250 μs. Thus, the response time of
the FBIS is sufficiently low to prevent the severe damage ofthe equipment.
References1) K. Yoshida, et. al., RIKEN Accel. Prog. Rep., 47, 169 (2014) .
2) M. Komiyama, et. al., RIKEN Accel. Prog. Rep. 41, 242(2008).
3) K. Yoshida, RIKEN Accel. Prog. Rep. 44, 131 (2011).
4) A. Yoshida, et. al., Nucl. Instr. and Meth. A521, 65 (2004).
5) A. Yoshida, et. al., Nucl. Instr. and Meth. A590, 204 (2008).
6) A. Yoshida, et. al., Nucl. Instr. and Meth. A655, 10 (2011).

Fig. 1 Logic diagram of the fast beam interlock system.
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RIKEN Nishina Center
FRIB/NSCL, Michigan State University- 207 -