Experimental Campaign With Superconducting Electron Cyclotron Resonance Ion Source At Van De Graaff, BARC S. C. Sharma#, J. A. Gore, N. Mehrotra, M. L. Yadav, R. N. Lokare, S. Goel, R. R. Sahu, N. K. Mishra, D. Sarkar, N. G. Ninawe, J. K. Yadav, R. S. Vishwakarma, Ramjilal, P. V. Gudekar, H. Sparrow, P. C. Bolar, S. K. Mohapatra, A. K. Gupta, B. K. Nayak, P. V. Bhagwat1 and A. Saxena NPD, BARC, Mumbai - 400085, 1IADD, BARC, Mumbai - 400085 Abstract (Electron Cyclotron Resonance) being operated periodically as per the BARC Safety Council regulatory permission Specific ion beams with different charge states were produced and mass analyzed to meet the diverse user requirements for the experimental campaign with stand-alone ECR ion source. These include; H+, 4He+q (q = +1 to +2), 14N+q (q = +1 to +7), 16O+q (q = +1 to +8), 20Ne+q (q = +1 to +7), 40Ar+q (q = +1 to +15) and 129Xe+q (q=+1 to +21). In addition, Deuterium ion beam was recently accelerated for the first time to study D-D reaction at 30 keV to 100 keV beam energy as part of low energy Nuclear Physics experimental measurements. The transverse emittance for specific ions of interest was also measured in situ. Experiments pertaining to measurement of cross sections for proton capture reactions, investigation on effect of irradiation on ultrafine grain Nb-Zr alloy and projectile X-rays spectroscopy are underway. This paper briefly describes the status of . Also, described are the typical control & instrumentation issues encountered and resolved during the round-theclock ECR source operation.
INTRODUCTION The superconducting ECR ion source equipped with 18 GHz, 2 kW RF power max [1], installed at Van-deGraaff, BARC, is being operated as per BARC Safety Council permission, periodically [2, 3], delivering various multiply charged ion beams, successfully. The three superconducting coils cooled by a cryogen-free single double stage cryo-cooler (4.2 K) provide the axial magnetic field whereas the multi-layer permanent magnets produce the radial magnetic field in the hexapolar configuration. The maximum installed at 18.0 GHz is. The maximum axial magnetic field achievable using this arrangement is Binj = 2.1 T and Bext = 1.37 T, whereas minimum Bmid = 0.4-0.6 T. Also the maximum radial hexapolar field is 1.32 T at the wall of 82 mm diameter plasma chamber. This source will be capable of delivering ion beams with high currents and high charge states over a wide mass range (1/7 ≤ q/m ≤ 1/2) across the periodic table, by ___________________________________________
#
[email protected]
using variety of source-feeds. The metallic beams can be generated using an oven (Tmax = 1400 ◦C) mounted with an angle of 50 with respect to the axis or via a sputtering system installed on the axis of the source. A cross-section of the ECR source is shown in Fig 1.
Figure1: 18 GHz Superconducting ECR Source with injection and extraction systems The beam extraction system consists of three electrodes in accel-decel configuration. The RF injection is through a direct WR62 waveguide separated from the RF amplifier via a 40 kV/2 kW dc breaker. A disk facing the plasma can be biased up to 1.2 kV. The extracted ions are mass selected and accelerated through the general purpose accelerating tubes before transporting to the experimental port. The ECR source system incorporates mass selection feature on the high voltage platform and is integrated with modern design concepts like RF direct injection, DC-bias moving disk, out-of-axis oven and axial sputtering facility, making this source more versatile. The ECR ion source shall operate in two modes. In one mode it will inject ions at 10 keV/A into the downstream accelerating elements. In the other mode, it will be a stand-alone facility, delivering ions right from protons to U34+, catering to the users from both basic and applied research.
The electrical consumption of full cryogenic system is about 7 kW. The cooling is ensured by a double stage 1.0 W at 4 K pulse tube cryo-cooler. The cold end of the pulsed tube is connected to a cold bus, which embeds and surrounds the three coils. A closed loop liquid Helium flow is maintained by a Helium compressor which itself is water cooled. Cooling down time is ~ 75 hrs to reach ~5 K, after getting high vacuum in the plasma chamber, as shown in Fig. 2.
located on the deck, thus introducing redundancy to the control & monitoring system. CONCLUSION
The 18 GHz superconducting ECR ion source has performed reliably producing specific multiply charged ion beams for various experimental campaigns, as per their yield and energy requirements, successfully. The stand-alone ECR source system is currently catering to the beam requirements of low energy multidisciplinary areas and shall also be used as an injector to downstream accelerating structure undergoing development.
ACKNOWLEDGEMENT The authors thankfully acknowledge the support of team members at Pelletron Accelerator Facility and IADD, BARC. Also, acknowledge the constant support and encouragement from Associate Director, Physics Group and Head NPD, BARC.
REFERENCES
Figure 2: Typical cooling down characterstics BEAM RESULTS
The charge state distributions for typical ion beams with different charge states were mass analyzed. These include; H+, 4He+q (q = +1 to +2), 14N+q (q = +1 to +7), 16 +q O (q = +1 to +8), 20Ne+q (q = +1 to +7), 40Ar+q (q = +1 to +15) and 129Xe+q (q=+1 to +21). In addition, Deuterium ion beam was accelerated to study D-D reaction at 30 keV-100 keV beam energy for carrying out measurements relevant to low energy Nuclear Physics. In addition, various experimental measurements pertaining to the cross sections for proton capture reactions of Astrophysical interest, investigation on effect of irradiation on nuclear waste glasses to assess the long term radiation stability and projectile X-rays spectroscopy were also performed, successfully. ECR CONTROL & MONITORING SYSTEM
The ECR control and monitoring system is Labview based. The interaction with the parameters in the frontend is through an ethernet link. The electronic devices are on a high voltage platform. The digitized parameter values are communicated via an ethernet link (through a PC located on the deck) to an ethernet to optical switch located on the platform. These values are optically transmitted to an optical to ethernet switch which is connected to a control PC. The control scheme was modified during this experimental campaign in a way that the control and monitoring software can be operated even from the PC
[1] G. Gaubert et.al, Pantechnik new superconducting ion source: PantechniK Indian Superconducting Ion Source, Rev. Sci. Inst. 83 02A344 (2012) [2] P.V. Bhagwat, A.K. Gupta et. al., Commissioning of PK-ISIS Superconducting ECR Ion Source at VanDe-Graaff, InPAC 2013, Nov 19-22, Kolkata [3] N. Mehrotra, S. C. Sharma et. al., Status Of Superconducting Electron Cyclotron Resonance Ion Source At Van De Graaff, BARC, InPAC 2015, Dec 21-24, Mumbai.
