Study of a new crystal array detector to measure double differential cross sections ofproton-actinide reactions in 600-MeV region
Y. Koba1, Z. Tsamalaidze2, P. Evtoukhovitch2, M. Imamura1, H. Iwamoto1, V. Kalinnikov2, W. Kallies2,N. Khomutov2, N. Kuchinski2, A. Moiseenko2, D. Mzavia2, V. Samoilov2, F.Tokio3, K.Kiyohara1, Y. Uozumi1, G. Wakabayashi1
1Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Motooka 744, Fukuoka 819-0395, Japan
Joint Institute for Nuclear Research, JINR, 141980 Dubna, Russia
3JAEA, 4-49 Muramatsu, Tokai-mura, Naka-gun, Ibaraki 319-1184, Japan
2Abstract. A new crystal array detector is proposed to conduct charged particle cross section measuremets with actinide targets fora study of accelerator transmutation of waste. The detector enables both the Time-of-Flight and the Pulse-Height measurements inan energy range around 600 MeV. From the simulation designs, it was revealed that the detector has great potential to realize amoderate energy resolution and a wide energy acceptance.

1 Introduction
The accelerator driven system (ADS) has been recognized as one of most
attractive options for the nuclear transmutation of high level nuclear waste.
One may expect ADS to reduce a hazard level of the waste dramatically,and to operate as an energy generator. Double differential cross section(DDX) data of nucleon-actinide reactions are of highly importance for thenuclear waste transmutation facilitated by ADS. In order to obtainhigh-quality nuclear data of DDX, one needs to use a detector that offers amoderate energy resolution of a few percent and a wide energy acceptancecovering from almost zero up to the maximum emission energy. Moreover,detection efficiency should be high enough for the usage of a thin target. Acrystal array detector is the most suitable one to these conditions, and theonly solution above 100 MeV. However, there are some crucial problems
when one uses it at energies of around/above 600 MeV.
In the present article are described a design study of a new crystal array
detector that combines the Time-of-Flight (TOF) and the Pulse-Height(PH) measurement.
2 Crystal array detector for charged particles
2.1 Difficulties of present methods
When one applies a crystal detector to measure charged particle energies
of several hundreds MeV, the particle identification (PI) analysis is mostuseful to deduce DDXs. However, the PI analysis is recognized to become
insufficient in a high energy range. This is because the peak efficiency, theratio of the number of full energy peak events to the total events, decreases
to a level where the PI analysis is no longer applicable.
Although TOF is effective to detect high energy protons, its efficiency
becomes very low due to a long flight path length that leads to an
extremely small solid angle and a large portion of beam bunchthinning-out in cyclotrons. Moreover, it is impossible to realize a wide
energy acceptance with a long flight path in charged particle
measurements under atmosphere.
2.2 Proposal of new detector system used in 600-MeV range
In order to meet the criteria discussed above, we propose a new detector
system which enables nuclear data measurement in a 600-MeV range. It
utilizes both the pulse height and TOF in proton measurements. As theconcept is illustrated in Fig.2, it consists of two sections; one is a crystal
detector based on the ordinal dE-E method, and the other the TOF section
following the crystal.
The crystal detector works as an E detector for low energy protons and an
energy degrader for high energy protons. Since low energy protons stop in
Inorganic
Scintillators

the crystal, one needs not the beam bunch thinning-out in cyclotron
operations. The shorter flight path length, which is realized by thedegrader, offers great advantages: the larger solid angle and easypreparation of a vacuum duct to cover the flight section which is essential
for charged particle measurements. The detector proposed presently isexpected to offer the best characteristics to fulfill required specifications,such as energy resolution and energy acceptance.
2.3 Energy resolution
The advantage of this method is demonstrated in Fig.2, which compares
the time of flight with/without the degrader crystal under the flight path
length of one meter. The effect of crystal degrader is significant, and helps
to improve the energy resolution.
3 Conclusion
A new type of detector system was studied to measure double differential
cross sections of proton productions from proton-actinide reactions ataround 600 MeV. The detector system is based on a combination of dE-E
and TOF measurements to realize a moderate energy resolution and an
extremely wide energy acceptance. On the base of simulation calculations,the detector arrangement has been optimized in terms of crystal
dimensions, TOF path length, and more.
References
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2 F. Saiho et al., Nucl. Instr. & Meth. A 537, 594 (2005).
3 Y. Uozumi et al., Journal of NUCLEAR SCIENCE andTECHNOLOGY, Supplement 2, 385 (2002)
4 T. Kin et al., Physical Revew C, Vol.72, 014606 1-9 (2005).
5 K. Anami et al., Nucl. Instr. & Meth. A 404, 327 (1998).
6 M. Imamura et al., Nucl. Instr. & Meth. A 564, 324 (2006).
7 Y. Koba et al., KEK proceedings 2006-7, Radiation Detectors and Their
Uses, 151 (2006).
8 Avdeichikov et al. Nucl. Instr. & Meth. A466, 427 (2001)

Plastic
Scintillator

Flight PathΔE

Ε , ΔETOFFig. 1. The detector arrangement we decided.

Fig.2. Estimated energy resolution as a function of proton energy
compared with/without crystal as energy degrader.