A. K. Sinha

HEAVY-ION REACTION ANALYZER (HIRA) - A RECOIL MASS SEPARATOR FACILITY AT NSC

An inter-university research facility [1] using a 16 MV tandem ion accelerator has been set up at Nuclear Science Centre (NSC), New Delhi. The heavy ion reaction analyzer (HIRA), a major experimental facility at NSC, is a large solid angle online mass separator for the reaction products preserving the kinematic correlation [2]. It is designed to effectively separate the nuclear reaction products of interest from the elastically scattered beam, dispersing them with good mass resolution at its focal plane with energy and space focusing. HIRA transports the ions within a short time (approximate to mu s) without losing the time correlation with the instant of reaction. The transit time spread (for a given energy) due to different flight paths is very small. With capability of operation over an angular range of -15 degrees to +40 degrees, HIRA is planned as a versatile reaction analyzer for heavy ion studies. The HIRA facility is operational and initial reports on its performance are presented [3]. In section 1 we give details of ion optical considerations and design goals. Section 2 gives some hardware details and results of field mapping of various magnetic components. The last section gives some of the results obtained in the preliminary measurements. A detailed description of the performance results of HIRA will be presented in a following publication.

A large high-energy gamma-ray spectrometer at NSC

Abstract A large NaI HIgh energy Gamma Ray Spectrometer (HIGRASP) has been designed and constructed at NSC, New Delhi. The spectrometer has been working quite satisfactorily for the last two years and has achieved the set goals. Detailed design considerations have resulted in very good energy resolution (2.5% at 22.5xa0MeV) and line shape of the gamma-ray spectrum. Experiments to study giant dipole resonance decay from hot rotating nuclei and nuclear Bremsstrahlung gamma emission have been successfully carried out using this spectrometer. The design, construction and response of the detector is discussed in detail.

A modular focal plane detector system for the heavy ion reaction analyzer at NSC, New Delhi

Abstract A detector system has been developed for the focal plane of the HIRA. It consists of two independent detectors, a low-pressure multiwire proportional counter (LP-MWPC) followed by a split-anode ionization detector. Details of the design and test results are presented. Using slow preamplifiers, the position resolution is 21 mm and the time resolution is estimated to be 1.5 ns for the LP-MWPC. The ionization detector gives 2.4% energy resolution for 150 MeV “Si scattered off a gold target and the AZ/Z obtained for 28Si+27A1 is l/42 for Z= 14. Some results for fusion and transfer studies for the 48Ti+58Ni and 28Si+68Zn systems, respectively, at energies around the Coulomb barrier, are presented to highlight the performance of the detector system. 1. Introduction Recoil mass spectrometers (RMS) are versatile tools for heavy ion reaction studies [ 1,2]. Coupled to a high rejection for beam-like particles is the excellent mass resolution with large solid angle, and space and energy focusing. They are ideally suited for studying reactions which are forward peaked and have found good application in the study of fusion and transfer reactions around the Coulomb barrier, spectroscopy by residue tagging, etc. The heavy ion reaction analyzer (HIRA) at the Nuclear Science Centre is a large solid angle RMS, details of which are presented elsewhere [3]. An important part of such spec- trometers is the focal plane detector system (see Refs. [4,5] and references therein). At the focal plane, the HlRA brings to focus particles of varying values of

Sub-barrier few-nucleon transfer reaction and channel coupling effects in heavy ion fusion

Measurements of sub-barrier transfer reactions are reported for the systems , and using the recoil mass spectrometer HIRA in kinematic coincidence mode. The problem related to M/Q-ambiguity in measurements with mass separators has been resolved. Excellent mass resultion with a large solid angle is obtained by correction of the aberrations. Simplified coupled-channels calculations are carried out for these systems with transfer form factors extracted from the measured transfer probabilities. The surface vibration coupling is treated up to two phonon states with second-order coupling terms.

Calibration of analyzing magnet for beam energy measurement using the recoil mass separator HIRA

Beam energy measurements have been carried out using the energy achromatic recoil mass separator HIRA at NSC. The energy was obtained from a measurement of the time-of-flight through HIRA which offers a flight distance of about 8.8 m. The method is quite useful for the calibration of the analyzer magnet over the entire operating range.