Present Status of RCNP-RING Cyclotron Facilities- Reference for Proposals -
This is a report of the RCNP-RING cyclotron and its experimental
equipment. The Research Center for Nuclear Physics (RCNP) is a
national nuclear physics laboratory with the RING cyclotron and the
AVF cyclotron. The RING cyclotron is in full operation and the
medium-energy nuclear physics programs is in progress at its
center. We hope that this report will be useful to write
experimental proposals.
A. Present status of beamThe type and quality of beams accelerated with the RING cyclotron are listed in the following.
High intensity beams are directly transported
to experimental halles from the AVF cyclotron. B. Present status of experimental equipment This is a summary of the experimental facilities. The users are encouraged to contact the following persons for technical details.
[1] High-resolution spectrograph: Grand Raiden (WS-course)The maximum magnetic rigidity is B_rho=5.66 Tm, and the momentum range is 5%. The maximum solid angle is 5.6 msr (design value), +- 20 mr for the horizontal acceptance angle and +- 70 mr for the vertical acceptance angle. There are two vertical drift chambers (effective length 1.2 m ) for general use as the focal plane position counters of the spectrometer. The position and angular resolution obtained from ray-tracing are 0.2 mm and 2.0 mr, respectively. It is possible to measure angular distributions of scattered particles from -5 deg to 90 deg. We have succeeded to measure 12C(p,p') at zero degree by decreasing the beam halo. By using dispersion matching techniques we obtained an energy resolution of 15 keV for 300 MeV protons and 20 keV for 400 MeV protons. We are developing experimental procedures and beam tuning techniques to perform high resolution measurements in a simpler way. In the scattering chamber there are three remote driving systems, target (up and down), a turntable with Faraday cup, and one general purpose turntable. Focal Plane Polarimeter (FPP) and a Dipole magnet for Spin Rotation (DSR) have been installed to measure polarization transfer reactions. Users are strongly encouraged to collaborate with the development group when performing an experiment with the FPP system.
[2] Neutron-TOF facility (N0-course)The length of the neutron flight path is 100 m at maximum and 10 m at minimum. Neutrons can be measured under the following conditions: 100 m flight path, 1/9 beam pulsing, and 50-60 MeV neutron detection threshold. The neutron detectors (neutron polarimeter) consist of four liquid scintillators (BC519, 1x1 m2, 10 cm thick), two plastic scintillators (BC408, 1x1 m2, 10 cm thick), and ten plastic hodoscopes (1m x 10 cm, 5cm thick). A spin rotation magnet,NSR, is used to measure neutron polarization in the scattering plane.There are two beam polarimeters and a scattering chamber for coincidence measurement (40 cm diameter) upstream from the swinger magnet. In the scattering chamber there are three remotely controlled driving systems, one for the target (up and down) and two general purpose turntables. Using these systems, it is possible to perform coincidence measurements of particles with neutrons at zero degrees. However, the background in the experimental hall has not yet been examined. The present status is summarized as follows:
[3] Heavy-ion secondary-beam course (EN-course)The secondary-beam course is a fragment separator for intermediate energy heavy-ion reactions. It consists of two dipole magnet systems and an energy degrader in-between. The reaction products at the first target point are isotopically separated and achromatically focused at the second target point. The primary beam can be injected onto the first target with a tilt angle of up to 8 degrees and thus spin-polarized secondary beams can be produced. The maximum magnetic rigidity of course is B_rho=3.2 Tm. The momentum acceptance is 4 %, and the angular acceptance is +- 20 mr for the horizontal angle and +- 14 mr for the vertical angle. The beam spot-size at the second target point is about 6.5 mm (horizontal) and 2 mm (vertical) in FWHM.The development of the secondary-beam course has been completed using primary 14N beams of 40 and 70 MeV/u. The reaction products of 12B and 8Li have been successfully separated with an isotopic purity more than 99%. A typical intensity of 12B was 2000 pps with the primary-beam intensity of 30 enA. [4] Large acceptance spectrograph (WS-course)The maximum magnetic rigidity is B_rho=3.2 Tm and the momentum acceptance is 30%. The maximum solid angle is about 20 msr, +- 60 mr for the horizontal and +- 100 mr for the vertical acceptance angle. It is possible to measure angular distributions of scattered particles from -10 to 125 degrees. At forward angles, smaller than 25 degree, the incident beam should be stopped at the Faraday cup inside the scattering chamber. The focal plane counter system consists of two vertical drift chambers (effective length: 1.7 m, effective height: 35 cm ) for ray-tracing and two planes of plastic scintillators for the trigger (200cm x 45cm, 6 mm thickness). In addition, twelve segmented scintillators (hodoscope) are available for the measurement of 2He or other two particles in coincidence.The parameters for trace-back have been established. It is possible to measure and analyze with a momentum resolution of 5x10-4 (including momentum width of beam), and angular resolution (FWHM) of 2 mr horizontally and 30 mr vertically. In the zero-degree measurements,if the momentum of the measured particle is about half of the incident beam momentum, we can transport the incident beam through the spectrograph and stop in an external beam dump.
[5] On-line computing facilitiesA on-line data acquisition system based on CAMAC Starburst and VAX (VAX4000/200, VAX station 3200, MicroVAX3500) is used in each experimental hall. The data transfer rates are more than 100 kbyte/sec, 300 cps for the Grand Raiden spectrometer, and 1 kcps for Neutron TOF. The Q-system developed at Los Alamos is used as on-line monitor system for experiments in the west and east experimental hall. Experiments in the neutron TOF course use an on-line monitor system developed at the Univ. of Tokyo. Users who are not familiar with each system are encouraged to contact the person in charge of each apparatus.Data are stored temporarily on hard disk in the VAX computer, and should subsequently be transferred to mass storage devices, 8mm magnetic tape, DAT, open reel and so on. [6] Off-line computing facilitiesOff-line computer system is an IBM p595 server which is partitioned to twovirtual machines. One is an interactive node which has 8 CPUs and 10 GB of memory. Other is a batch node which has 32 CPUs and 122 GB of memory. The performance of each CPU is 2796 SPECfp2000. Each node can access to 200 TB of disk storage system with performance of 24/14 Gbps reading/writing 16 files concurrently. Required capacity of the disk storage will be assigned to each experimental group by "storage managers". To access to the computer system from the internet, you should use our login server or file transfer server. A new off-line computer system will replace existing system in August 2010. |
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