Isotopically enriched boron targets of a typical thickness 1.8 mg/cm2 were fabricated on polymer (polypropylene and Mylar) backing using the sedimentation method. Polyvinyl alcohol (PVA) was used as a binder in this target preparation. It was observed that without including an additional PVA layer, boron spills off during ion beam exposure. Adding a PVA layer may produce defects in target, which were identified and discussed. Targets were characterized for thickness uniformity, surface defect and elemental purity using alpha- spectroscopy, optical microscopy, Fourier Transform Infrared spectroscopy (FTIR) and X-ray diffraction (XRD) techniques. Ion beam experiment shows that polypropylene-backed targets are more prone to degrade during beam exposure. No such effect was observed for the target with Mylar backing instead of having a higher thickness than polypropylene.

At the Inter University Accelerator Centre, a high current injector programme (HCI) is being developed as an alternate injector to the superconducting linear accelerator (SC-LINAC). For this purpose, a high temperature superconducting ECR ion source, PKDELIS, based on Gifford McMahon cryocoolers was designed, installed and commissioned in the Low Energy Beam Transport section of the high current injector. The ion source will inject multiply charged ions having A/q similar to 6 for further acceleration into the downstream RFQ and DTL accelerators before final injection into the superconducting linear accelerator. The details of the design, and experimental results of the ion source together with performance of the cryocoolers are presented in this paper.

The superconducting heavy ion linear accelerator at Inter-University Accelerator Centre Delhi has been in operation since 2007. Initially, the superconducting niobium Quarter Wave Resonators (QWRs) in the linac were phase locked using a combination of electronic and mechanical controls which operated in fast (~10 μsec) and slow (~sec) time scales respectively. In this scheme, fast control was achieved through dynamic phase control whereas slow control of the frequency was done through the niobium tuner bellows installed at the drift tube end of the resonator and flexed using helium gas to change the resonance frequency. In order to improve the dynamics of this control system, an alternate scheme using piezoelectric actuator, instead of helium gas, to flex the same niobium bellows, has been implemented in the QWRs of the second and third accelerating modules of the linac. The piezoelectric actuator is used in closed loop along with the fast dynamic phase control scheme. The feedback loop of the piezoelectric control includes a dual control scheme - an integral control loop to arrest the slow drift, and the positive position feedback (PPF) based control loop to damp the microphonics. This control scheme has been found to arrest slow drifts in the resonator frequency more tightly along with damping of low frequency microphonics (~few tens of Hz) picked up by the resonator from its surrounding environment. This has substantially eased the load from the fast electronic control, resulting in the reduction of the radio frequency (RF) power requirement during operation. In addition, it has improved the stability of phase and amplitude of the QWRs. The details of the new scheme along with results obtained during the online run of the linac for beam acceleration are presented.

The effect of the frequency tuning on bremsstrahlung spectra, beam intensity and shape in the 10 GHz, Nanogan ECR ion source have been investigated. The main aim of this work was to study the effect on a lower frequency type of ECR source where the separation between various modes in the cavity is much larger. The warm and cold components of the electrons were observed to be directly correlated with the beam intensity enhancement in the case of Ar but not so for O. However, the warm electron component was much smaller than the cold component. The beam shapes of O measured as a function of frequency showed a strong variation without hollow beam formation. Due to the use of an octupole magnetic structure in the Nanogan ECR source, the quadrupolar structure of the ECR surface is modified with the frequency tuning. In general, we have observed a strong absorption of microwave power at various frequencies whenever the reflection co-efficient showed a minimum value and the effect was seen stronger for the higher charge states. Details of the measurements carried out on the bremsstrahlung spectra, beam intensity and shape are presented together with the results of simulations.

There is a growing demand for a high brightness light source with short pulse length among the researchers in the field of physical, chemical, biological and medical sciences in India. To cater to the experimental needs of multidisciplinary sciences, a project to develop a compact Light Source has been initiated at Inter University Accelerator Centre (IUAC). In the first phase of the project, pre-bunched electron beam of ~ 7 MeV energy will be generated by a photocathode RF gun and coherent THz radiation will be produced by a short undulator magnet. In the next phase, the energy of the electron beam will be increased up to 40 MeV by a pair of superconducting niobium resonators. The coherent IR radiation will be produced by using an undulator magnet (conventional method) and X-rays by Inverse Compton Scattering. To increase the average brightness of the electromagnetic radiation, fabrication of superconducting RF gun is going to be started in a parallel development. In this paper, the design of the accelerator system and the plan of producing THz radiation will be discussed.

The ion current achievable from high intensity ECR sources for highly charged ions is limited by the high space charge. This makes classical extraction systems for the transport and subsequent matching to a radio frequency quadrupole (RFQ) accelerator less efficient. The direct plasma injection (DPI) method developed originally for the laser ion source avoids these problems and uses the combined focusing of the gap between the ion source and the RFQ vanes (or rods) and the focusing of the rf fields from the RFQ penetrating into this gap. For high performance ECR sources that use superconducting solenoids, the stray magnetic field of the source in addition to the DPI scheme provides focusing against the space charge blow-up of the beam. A combined extraction/matching system has been designed for a high performance ECR ion source injecting into an RFQ, allowing a total beam current of 10 mA from the ion source for the production of highly charged (238)U(40+) (1.33 mA) to be injected at an ion source voltage of 60 kV. In this design, the features of IGUN have been used to take into account the rf-focusing of an RFQ channel (without modulation), the electrostatic field between ion source extraction and the RFQ vanes, the magnetic stray field of the ECR superconducting solenoid, and the defocusing space charge of an ion beam. The stray magnetic field is shown to be critical in the case of a matched beam.

Studies on the effect of the frequency tuning on the bremsstrahlung spectra, beam intensities, and beam shape of various ions have been carried out in the 10 GHz NANOGAN ECR ion source. The warm and cold components of the electrons were found to be directly correlated with beam intensity enhancement in case of Ar(9+) but not so for O(5+). The warm electron component was, however, much smaller compared to the cold component. The effect of the fine tuning of the frequency on the bremsstrahlung spectrum, beam intensities and beam shape is presented.

The temperature stability of the conduction-cooled or cryogen-free magnet is governed by the heat balance between the heat generation rate and the cooling rate by the cryocooler through the thermal links. The dynamic thermal profile of a conduction-cooled NbTi magnet during charging and discharging process has been analyzed in terms of theoretically evaluated dynamic heat loss profile. The NbTi coil was energized up to 90 A with 2 A/min, 4 A/min, and 6 A/min sweep rates and the corresponding hysteretic AC loss and resistive heat loss have been estimated with all three sweep rates. The equilibrium temperatures of the magnet are 3.23 K and 3.82 K at zero and 90 A current respectively. At the beginning of the charging process, the AC loss has dominant role in the thermal profile of magnet but resistive heat loss takes over the dominant role towards the end of charging process. The thermal profile of the magnet during continuous charging has been compared with discharging of the magnet and step-wise charging. (C) 2012 Elsevier Ltd. All rights reserved.

Plasma potentials for various heavy ions have been measured using the retarding field technique in the 18 GHz high temperature superconducting ECR ion source, PKDELIS [C. Bieth, S. Kantas, P. Sortais, D. Kanjilal, G. Rodrigues, S. Milward, S. Harrison, and R. McMahon, Nucl. Instrum. Methods B 235, 498 (2005)10.1016/j.nimb.2005.03.232; D. Kanjilal, G. Rodrigues, P. Kumar, A. Mandal, A. Roy, C. Bieth, S. Kantas, and P. Sortais, Rev. Sci. Instrum. 77, 03A317 (2006)10.1063/1.2164887]. The ion beam extracted from the source is decelerated close to the location of a mesh which is polarized to the source potential and beams having different plasma potentials are measured on a Faraday cup located downstream of the mesh. The influence of various source parameters, viz., RF power, gas pressure, magnetic field, negative dc bias, and gas mixing on the plasma potential is studied. The study helped to find an upper limit of the energy spread of the heavy ions, which can influence the design of the longitudinal optics of the high current injector being developed at the Inter University Accelerator Centre. It is observed that the plasma potentials are decreasing for increasing charge states and a mass effect is clearly observed for the ions with similar operating gas pressures. In the case of gas mixing, it is observed that the plasma potential minimizes at an optimum value of the gas pressure of the mixing gas and the mean charge state maximizes at this value. Details of the measurements carried out as a function of various source parameters and its impact on the longitudinal optics are presented.

3D simulation studies using RADIA code have been performed to optimise the magnetic holes in the high temperature superconducting electron cyclotron resonance (HTS-ECRIS) ion source for improving the extraction efficiency and intensities of highly charged ions. The magnetic field improvements using simple techniques like optimisation of iron regions is found to be economical. The extraction efficiency can be increased three-fold in the case of a hexapole magnet depending on the level of the uniformity of the fields in the high and low regions. This technique further minimises localized heating of the plasma chamber walls which can improve the vacuum conditions in an ECR ion source. For superconducting sources where the x-ray heat load poses severe problems during operation, such a reduction of heating load is of great significance. The typical triangular pattern of the plasma impact observed on the plasma electrode of HTS ECRIS at various tuning conditions are reproduced by the simulations. Details of the simulations and experimental results will be presented.

The design and implementation of a purely electrostatic deceleration lens used to obtain beams of highly charged ions at very low energies is presented. The design of the lens is such that it can be used with parallel as well as diverging incoming beams and delivers a well focused low energy beam at the target. In addition, tuning of the final energy of the beam over a wide range (1 eV/q to several hundred eV/q, where q is the beam charge state) is possible without any change in hardware configuration. The deceleration lens was tested with Ar(8+), extracted from an electron cyclotron resonance ion source, having an initial energy of 30 keV/q and final energies as low as 70 eV/q have been achieved.

The facility for constructing superconducting niobium resonators indigenously was commissioned at the InterUniversity Accelerator Centre in 2002. It was primarily setup to fabricate niobium quarter wave resonators for the superconducting booster linac. Starting with a single quarter wave resonator in the first phase, two completely indigenous resonators were successfully built, tested and installed in the cryomodules. Subsequently production of fifteen more resonators for the second and third modules began. Several existing resonators have been successfully reworked and restored from a variety of problems. In addition to building resonators for the in-house programs, a project to build two single spoke resonators for ProjectX at Fermi Lab, USA has also been taken up. A Tesla-type single cell cavity is also being built in collaboration with RRCAT, Indore. This paper presents details of the fabrication, test results and future plans.

For the high current injector project at Inter University Accelerator Centre, a high temperature superconducting electron cyclotron resonance (ECR) ion source, PKDELIS, would provide the high charge state ions. The emittance of the ECR ion source is an important parameter to design further beam transport system and to match the acceptances of the downstream radio frequency quadrupole and drift tube linac accelerators of the high current injector. The emittance of the analyzed beam of PKDELIS ECR source has been measured utilizing the three beam size technique. A slit and two beam profile monitors positioned at fixed distances from each other were used to measure the beam size. The digitized beam profiles have been analyzed to determine the emittance of various multiply charged ions. The variation of emittance with gas mixing, ultrahigh frequency power, and extraction energy are discussed in this presentation.

Hybrid recoil mass analyzer (HYRA) is a unique, dual-mode spectrometer designed to carry out nuclear reaction and structure studies in heavy and medium-mass nuclei using gas-filled and vacuum modes, respectively and has the potential to address newer domains in nuclear physics accessible using high energy, heavy-ion beams from superconducting LINAC accelerator (being commissioned) and ECR-based high current injector system (planned) at IUAC. The first stage of HYRA is operational and initial experiments have been carried out using gas-filled mode for the detection of heavy evaporation residues and heavy quasielastic recoils in the direction of primary beam. Excellent primary beam rejection and transmission efficiency (comparable with other gas-filled separators) have been achieved using a smaller focal plane detection system. There are plans to couple HYRA to other detector arrays such as Indian national gamma array (INGA) and 4 π spin spectrometer for ER tagged spectroscopic/spin distribution studies and for focal plane decay measurements.

X-ray bremsstrahlung measurements from the 18 GHz High Temperature Superconducting Electron Cyclotron Resonance Ion Source, Pantechnik-Delhi Ion Source were measured as a function of negative dc bias voltage, keeping all other source operating parameters fixed and the extraction voltage in the off condition. The optimization of medium and highly charged ions of argon with similar source operating parameters is described. It is observed that the high temperature component of the electron is altered significantly with the help of bias voltage, and the electron population has to be maximized for obtaining higher current.

The superconducting heavy ion LINAC at the Inter University Accelerator Centre (IUAC) is designed to have three accelerating modules, each housing eight Niobium Quarter Wave Resonators (QWR), a superbuncher housing a single QWR and a rebuncher housing two QWR's. Presently one accelerating module, the superbuncher and the rebuncher are operational. The other two modules are in an advanced stage of fabrication. In a recent operation several ion beams (from 12 C to 107Ag) from the 15 UD Pelletron were further accelerated through the first LINAC module and delivered for scheduled experiments. The energy gain from the LINAC, which was primarily dictated by the requirements of the experiment, was in the range of 2.5- 3.5 MeV per charge state. The time widths achieved at the LINAC entrance and at the target locations were of the order of 200 and 350ps respectively. Details of the operational experience, results, problems encountered and the improvements that are being planned, have been presented in the paper.

The feasibility and utility of a Helium multi-jet system to transport fission fragments vertically up to an ion source 50 m above ground level is explored. This idea opens up the possibility of using the existing 15-UD tandem and SC linac accelerator system at Inter University Accelerator Center (IUAC) as a post accelerator for rare isotope beams (RIBs). This could considerably speed up the upgrade of the facility to a RIB facility since the driver accelerator (e.g. a 50 MeV electron accelerator) can be purchased. We find that such a facility will be competitive for refractory neutron-rich isotopes and can later be combined with a positive ion injector to produce a large number of beam species with higher intensities.

A superconducting linear accelerator based on niobium quarter wave resonators has recently become operational to boost the energy of the heavy ion beams available from the existing 15 UD ( unit doubled) Pelletron accelerator. The niobium resonators typically performed at an accelerating field of 3-6 MV/m at 6 watts of input power in the test cryostat. When they were tested in the linac cryostat, the accelerating fields were drastically reduced and a number of other problems were also encountered. At present, all the problems have been diagnosed and solved. Many design modifications, e. g., in power coupler, mechanical tuner, helium cooling system, etc. were incorporated to solve the problems. A novel method of vibration damping was also implemented to reduce the effect of microphonics on the resonators. Finally, the accelerated beam through linac was delivered to conduct experiments.