1. Improved performance of Variable Energy Cyclotron(VEC) Variable Energy Cyclotron Centre Kolkata P S Chakraborty, B Ch Mandal, S K Thakur, M Das, S Som, S Pal, G Pal, S Saha, C Mallik and R K Bhandari Theme Meeting on Unveiling Future with Cyclotrons, June 28-29, 2012, VECC

2. Introduction The first internal beam : 16 th June, 1977 Accelerated particles : alpha, proton & deuteron with internal PIG Ion Source.

3. Contd.. Accelerated particles : Light heavy ions like oxygen, nitrogen, neon & argon of various charge state with external ECR Ion Source.

4. Contd.. The Variable Energy Cyclotron (VEC) after accelerating high charge state light heavy ions for about 10 years was shut down in early 2007 for upgradation, modification and modernisation of cyclotron sub-systems. Modernization program was essential because most of the cyclotron sub-systems were prone to failure frequently as these systems were very old and their maintenance was also getting difficult as spares were not readily available.

5. Aim To upgrade and modernize various sub-systems for achieving improved performance in terms of smooth and un-interrupted operation of cyclotron and experiment as well. To make suitable modifications in the central region for light ion (alpha, proton) acceleration as this cyclotron will be used as primary source of beams for Radioactive Ion Beam facility.

6. Modernization activities The cyclotron centre region for heavy ion acceleration shown below has been modified for incorporating internal PIG ion source to produce alpha and proton beams. Central region for heavy ion acceleration (Top view)

7. Contd.. The PIG ion source can also be replaced by the inflector system for high charge state heavy ion beam acceleration, produced in an ECR ion source, after making minor modifications in the central region. Modified central region for light ion acceleration (Top view)

8. Contd.. The operation of the magnet power supplies (main magnet, trim coils, quadrupole magnets, steering magnets, switching magnet) are made computer control. The relay-based interlock system has been up-graded by the PLC based safety interlock system for RF operation. MMI interface showing three HI beam lines and the feeder line leading to RIB facility Touch panel with digital knobs at control console

9. Contd.. Up-graded to PLC based control of vacuum system operation is working satisfactorily. Major modifications in control console incorporating computerized control of most of the sub-systems. The operator interface of the systemModified control room

10. Contd.. New vacuum chamber of 159.5 degree analyzing magnet has been installed through which beam has been transported in achromatic mode to the radio-active ion beam facility. Analyzing Magnet and beam lines Feeder line leading to RIB facility

11. Synchronized operation of various sub-systems of cyclotron started on November,2009. Internal beam was developed in the middle of December,2009. Extracted beam of 35 MeV alpha was obtained in January,2010. Synchronization Cyclotron, beam lines and extracted beam

12. Utilization The first experiment after modernization program started on 8 th February, 2010. In the year 2010-2011 and 2011-2012, the cyclotron has delivered alpha and proton beams for more than 3000 hours for the experiments.

13. Projectiles Presently cyclotron is delivering the following ions for performing experiments. Ions Energy (MeV) Extracted beam current (µA) Alpha 30 - 65 20.0 Proton 7.5 - 20 28.0

14. Experiments Nuclear physics in Channel # 2 and 3 Radio-chemistry and Material science in Channel # 1 Producing of radio-active isotopes in feeder beam line Experimentalists: VECC, BRIT/VECC Saha Institute of Nuclear Physics RchD/BARC, AchD/BARC, MMD/BARC UGC-DAE-CSR, Kolkata Kyungpook National University, Korea

15. Operating diagram of VEC

16. Future Program One of the major problems leading to the downtime of cyclotron operation has been water leak in the RF cavity components. The leaks in the RF panel are often tackled quickly while leaks in the dee, dee stem shown below consume considerable time to come back to operation. The source of the problem is a brazing leak in the cooling lines. Dee stem skin cooling loop

17. Contd.. Over the years, the surface characteristics of the entry electrode of deflector shown above have deteriorated resulting in problems of high voltage holding capacity. For this, a new set of deflector electrodes is under fabrication. Deflector electrodes

18. Performance Improved performance of cyclotron In terms of beam tuning: Setting the operational parameters from archive produces accelerated extracted beam with minor tuning within a very short time. In terms of identifying the fault of any system: Display of all the parameters together helps in identifying the system malfunctioning. The stability of beam has been improved greatly after modernization activities.

19. Contd.. Beam current on target

20. Conclusion Smooth and un-interrupted experiment for hours. Beam current delivered on target up to 10 µA as per user’s requirement. Maximum beam current obtained mentioned earlier is not with the full efficiency of ion source. Incorporating new RF cavity components will greatly reduce the cyclotron down time. Incorporating new extraction electrodes will enable us to extract higher beam energy.