HIRA-INGA FACILITY AT NSC
The installation of the Indian National Gamma Array (INGA) coupled to the recoil mass separator HIRA at NSC was successfully completed in November, 2002 in collaboration with universities and other institutes. The Clover detectors along with associated electronics were pooled from IUC-DAEF, SINP, TIFR, BARC, VECC and NSC.
A mechanical structure to mount up to eight Clover detectors around the target location of HIRA was fabricated which could also accommodate four neutron detectors for neutron-gated spectroscopy. The Charged Particle Array from TIFR was installed in the beamline for additional channel selection. The energy and timing information from all the detectors were recorded event by event using the multi-crate data acquisition system CANDLE. A compact high-density module has been developed in-house for processing of energy and timing information from the individual detector segments.
INGA facility at NSC
With a typical g - g coincidence data rate of 2-3k/s, around 109 events were recorded per experiment in six days of beam time. Apart from two and higher fold coincidences, mass gating, neutron gating and charged particle multiplicity gating were used successfully for improved channel selection.
About sixteen experiments were completed by different groups from all over the country during the period Nov, 2002 to May, 2003. These experiments were aimed at probing a wide variety of nuclear structure phenomena such as, magnetic rotation, chirality in nuclei, properties of f-p shell nuclei, super-deformed bands and n-p interaction in N=Z nuclei. The facility was also effectively used for isomer tagging experiments. A large number of faculty and students from the various universities, colleges and institutions participated in these experiments.
INGA Workshop : NSC organized a one day workshop on Nuclear Physics with INGA on September 16, 2003. The prime focus of the workshop was to discuss the results obtained from the series of INGA experiments executed at NSC. The workshop was attended by all collaborators and a few young faculty members and students from various institutes and universities. A total of 14 reports were presented on the experiments performed at NSC. A few talks were delivered by the concerned persons on the topic of nuclear spectroscopy at energies well above the Coulomb barrier.
At the end, open discussion was held among the collaborators on the possible improvements of the experimental facilities and planning new experiments for future. It was decided to hold the next series of INGA experiments at VECC, Kolkata in early 2004 using the heavy ion beam from VECC Cyclotron.
Status of INGA Electronics modules : After successful testing of two prototype units of INGA electronics modules with INGA + HIRA setup at NSC, production of 12 such modules for future applications have been undertaken. Meanwhile, the technical staff from SINP, Kolkata are getting trained by duplicating 2 such modules. Altogether 14 modules would be available for use by the end of November 2003 after completion of testing.
Workshop on Physics with Neutron Array (June 10, 2003) : The Nuclear Science Centre along with Panjab University and a few others has just completed the assembly of an array of 8 neutron detectors along with pulse shape discriminators to be used as time of flight spectrometers, with DST funding. A workshop was held at NSC on June 10, 2003 to bring together interested research groups to explore what interesting physics research may be carried out with this array which may be augmented by adding other similar detectors available in the country. The workshop was attended by about 20 outside participants from BARC, VECC, Delhi University, Panjab University, BHU, AMU, Karnatak University, Guwahati University and GB Pant university, in addition to a number of NSC participants. Introductory remarks were given by Prof. V.S. Ramamurthy, Secretary of DST. Six other speakers talked about various aspects of research and a group discussion was held at the end. The topics discussed included : Fission and dissipation measurements with neutron measurements, entrance channel effect studies, gamma spectroscopy with neutron detector filters and neutron mesurement at intermediate energies. A committee was constituted to go into plans for future research with an extended array and building a new chamber for neutron array research in one of the beam lines in phase II beam hall.
BEAM TEST THROUGH LINAC CAVITIES
In beam hall II, the zero degree beam line has been recently extended from first LINAC cryostat to the second switching magnet. All the magnets and other diagonostic elements have been installed and properly aligned with a high precision theodolite (Leica make). The cables from beam hall II to control room has been laid out for remote CAMAC control and status display of the various components upto the switching magnet. Four superconducting Niobium resonators alongwith a superconducting solenoid magnet had been properly aligned and installed inside the first cryostat to test their performances with beam. DC Nickel beam and pulsed silicon beams from Pelletron were transmitted through the four resonators and a solenoid magnet (non-energised) upto a scattering chamber located at the the entrance of the switching magnet. The transmission of the beam from FC 04 in vault-I (just after the Analysing magnet) to FC 07 in vault- II (before second switching magnet) was found to be ~ 100%. The performance of the Multi-harmonic buncher (MHB) installed before Pelletron tank and High energy sweeper (HES) after Analysing magnet was found to be satisfactory. The time structure of pulsed Si beam produced by MHB and HES was measured to be ~2 ns ( FWHM) and no drift was observed for two hours. The dark current introduced by the MHB was eliminated almost entirely by the HES. The coarse adjustment of the slits and voltage of HES had improved the peak to dark current ratio (PDR) from 60% (when only MHB is operated) to 90% (when MHB and HES both are operated). Better adjustment of the slits and voltage would improve the PDR. An extensive testing of resonators alongwith solenoid magnet is being planned in November/December by accelerating pulsed beam from super-buncher. First time offline testing of four cavities together, inside the linac cryostat at 4.5 K, were successfully carried out by closed loop cooling through liquid helium distribution network. The test continued for six days and major controlling and monitoring parameters were monitored through cryogenic control room. This test can be treated as a prequalifying test with respect to cryogenics, resonator performance and resonator controller electronics prior to final beam test. The solenoid magnet was also energised (upto 7 Tesla) successfully at 4.5 K with current lead cooling by cold helium gas. Noises on temperature reading by DT470 silicon diode sensor were observed with RF field particularly after crossing the multipactoring barrier. This problem would be sorted out prior to proposed beam test in November/December, 2003.
LOW ENERGY ION BEAM FACILITY
Various ion beams are regularly being delivered using electron cyclotron resonance (ECR) ion source based low energy ion beam facility for experiments in materials science and atomic physics at Nuclear Science Centre (NSC) . ECR ion source placed on high voltage platform (200 kV) is capable of producing positive ions in high charged states from practically all species. Most metals have low vapor pressure at quite high temperature and production of high intensity beam by conventional methods like micro-oven, sputter gun, insertion method is quite difficult. We have designed and installed MIVOC (Metal Ion by VOlatile Compound) facility on high voltage platform to produce beams of materials having low vapor pressure at high temperature. Higher temperatures are detrimental to the properties of permanent magnet used for radial as well as axial confinement of plasma in Nanogan type of ECR ion source. In the insertion method a thin wire of material is injected into the plasma which cools the plasma locally at the point of injection and creates plasma instabilities. Since volatile compounds have vapor pressure of greater than 10 -3 mbar at room temperature, an elegant solution of this problem is to switch over to MIVOC method, in which vapors of volatile compounds having metal atoms in their molecular structure are used to release metallic elements. This facility consists of a small chamber and a vapor flow control valve together with the control unit. The MIVOC chamber containing volatile compound is connected to the injection side of ECR ion source from where the vapor of compound is allowed to diffuse into the source. Decomposition and ionization of the compound then take place in the plasma. The MIVOC system is set-up successfully and is being used regularly. Iron beam is produced using ferrocene [ Fe ( C5H5 ) 2 ] having vapor pressure of 1.7 x 10-3 torr at 200C. The Fe+ beam was used to study the Fe nano-phase formation inside various matrices. Using MIVOC, we got 200 keV Fe+ beam of 8 mA. We have used chlorotrimethylsilane [ Si(CH3)3 Cl ] to extract the Si ion beam for synthesis of embedded Si nano structure inside various host matrices.
MIVOC facility coupled to ECR system
Apart from existing 900 beam line which is dedicated to the materials science related experiments, another 150 degree beam line is also set-up to study the interaction of ion beams to liquid droplets target. All beam line components like quadrupole doublet, quadruople triplet, double slits, droplet chamber etc are fabricated indigenously. For the beam test, Ar+2 200 keV@10mA was transmitted through the 150 beam line and a fine circular spot of approximately 2mm diameter was seen on the quartz mounted on the beam line at the position of the center of droplet chamber.
A National workshop on Design of Innovative Experiments for Post Gradate Teaching Laboratories was held on Sept.4-6, 2003, in order to chalk out future course of action for NSC, as how best to provide help to teaching laboratories (post graduate) in the universities and colleges in order to arrest the decline of student interest in experimental physics. The workshop was inaugurated by the Honourable Minister of Human Resources Development, Prof. M.M. Joshi and was attended among others, by distinguished guests and educationists, e.g. the UGC Chairman, Prof. A. Nigavekar, Vice Chairman, Prof. R.S. Pillay, Prof. S.Lokanathan, Prof. Yash Pal, Prof. G.K. Mehta etc. The keynote address was delivered by the famous pioneer in the field of upgrading of PG lab experiments, Prof. B.L. Sharaf. The director of Centre for Development of Post Graduate Education in Jaipur, Prof. B.K. Sharma and his colleague Dr. Y.K. Vijay also participated. Among the speakers were such noted leading exponents of the field e.g. Prof Somenath Datta, Prof.A.W. Joshi, Prof. P.C. Jain and Dr. Rajesh Kharpade.
There were 23 talks given by the participating teachers. Many of these were supplemented by demonstrations. Several novel experiments were also performed. A low cost data acquisition system including pre-amplifier, amplifier and ADC, a general purpose instrumentation board (used to measure I-V characteristics of a diode for instance) and a charged particle detector using a photo-voltaic device , all developed by NSC, were put on display. A spark counter, an experiment on Laser diffraction, experiments in solid state physics, beta solenoidal spectrometer, Linear air track for collision studies were some of the experiments demonstrated. There was a lively discussion session on the future role of NSC in this field.
RADIATION DETECTOR WORKSHOP
a one day workshop on Radiation detectors on March 14, 2003. This workshop
was the first of its kind by NSC in bringing together various researchers
working in the field of development of radiation detectors and new materials.
52 participants from universities and other institutes registered for the
workshop. The proceedings included invited and contributed talks from various
researchers on topics covering gaseous detectors, charged particle detectors,
GaAs, InP and CdZnTe detectors, and clover detectors.
WORKSHOP ON RADON STUDIES IN ENVIRONMENT
Due to growing interest in applications of radon studies viz. in earth sciences, helium exploration, radiation protection, dosimetry and risk analysis on radon/thoron and health sciences, a workshop on radon studies in the environment was organized on 24th February 2003. The topics discussed in this workshop were quite beneficial to the universities. The application of radon studies in earth sciences like in earthquake prediction, in volcanic surveillance, mineral exploration, and geothermal energy production were also covered in this workshop. The seismicity in Delhi and adjoining areas has been attributed to the intersection of various lineaments and ridges. The radon studies in this area will provide good data for the earth sciences. NSC being an inter-university research facility of UGC, will act as a focal point for radon studies in the universities and a limited support will be given to them. There were around 10 universities which participated in this workshop. Two research institutes BARC and VECC also participated.
NSC Acquaintance Programmes
NSC acquaintance programs have been held at Guru Ghasidas University, Bilaspur and H.N.B. University, Garhwal in the current year. Different beam line facilities and research programs of NSC were highlighted in these programmes, which generated a lot of interest among the participants from different colleges and Universities in and around the chosen locations.
The first one was held at School of Pure and Applied Physics, Guru Ghasidas University, Bilaspur on July 26th, 2003. It was attended by nearly 30 faculties from universities of Bilaspur, Nagpur and Raipur and their affiliated colleges. It was also attended by 30 students from the university, engineering college and their affiliated colleges.
The second acquaintance programme, organised in the HNB Garhwal University was on 10th October, 2003 at the New Tehri campus. The local organiser was the Department of Physics, HNB Garhwal University. It was the first of such programmes organised in the state of Uttaranchal. There were two talks delivered by the NSC resource persons. The first talk dealt with Pelletron and its uses in Nuclear Physics, Materials Science and AMS, and the second talk dealt with Heavy Ion Radiation Biology. The talks were followed by a feed back and open discussion session. The day long programme was attended by about one hundred participants comprising of faculty members from various colleges and universities of Uttaranchal.
Next ones are scheduled at M.L.Sukhadia University (Udaipur) and at Patna University on 15th and 25th November, 2003 respectively.
RECENT CIVIL WORKS
The actual construction of NSC Phase II- Part II, stage 1 has started with effect from May 2003. It includes the following buildings :-
* Lab. 1-Material
The construction of the above is likely to be completed by September 2004. A small building namely Beam Hall II extension was earlier completed in February 2003.
Status of Pelletron
The machine ran reasonably well during this period of six months (April 1 to Sept.30, 2003). Multi-harmonic buncher is being regularly used to provide pulsed beam to user with good stability and high efficiency. The problem of Ion Source General Purpose tube, not holding voltage above 190 kV, was solved by baking the GP tube and it is holding the usual voltage of 250 kV now. Four damaged column support posts in unit #10 were changed. There were two tank openings within this period.
Hours = 3341 Hrs.
/Institute - No. of Shifts Utilized
Nuclear Science Centre, Aruna Asaf Ali Marg, JNU (New) Campus, New Delhi
Phone: 91-11-26893955, 26892601, 26892603 ; FAX : 91-11-26893666