CYCLOTRONS 2010 - List of Authors (De, A.)

Paper	Title	Page
MOPCP009	Development of Power Supplies for 3-Ф, 240 kW RF System with Crowbar Protection for Superconducting Cyclotron at VECC	60
	S.K. Thakur, R.K. Bhandari, A. De, Y. Kumar, J.S.P. Prasad, S. Saha, S.S. Som, T.P. Tiwari DAE/VECC, Calcutta, India
	RF system of K-500 super conducting cyclotron at VECC is a complex three phase system operating in the frequency range of 9 MHz to 27 MHz with maximum acceleration potential of around 100 kV feeding to each of three Dee cavities placed in median plane of cyclotron 120° apart through coupling capacitors. Each phase consists of chain of amplifiers and resonator operating in synchronization and at final stage of each phase, a high power water cooled Tetrode Tube (Eimac 4CW 150,000 E) as an RF high power amplifier each capable of delivering 80 kW of RF power. Individual power supplies for biasing Anode (20 kV, 22 Amp), Filament (16 V, 225 Amp), Screen (1600 V, 1 Amp) and grid (-500 V, 0.1 Amp) each for all three high power Tetrode Tubes are designed, developed and commissioned indigenously in VECC Cyclotron building and have been in operation from last few months successfully. Anode supply is common to all three tubes, rated at 20 kV, 22 Amp, 450 kW along with fast acting crowbar protection using Ignitron. This paper describes about the technical challenges in the development of the power supplies and special features of protection systems.

MOPCP095	Experiment and Analysis: Partial Loss of Insulation Vacuum in K-500 Superconducting Cyclotron During Energization	248
	P. Bhattacharyya, M. Ahammed, S. Bandyopadhyay, R.K. Bhandari, U. Bhunia, J. Chaudhuri, A. De, A. Dutta Gupta, C. Mallik, A. Mukherjee, C. Nandi, U. Panda, S. Saha, S. Saha DAE/VECC, Calcutta, India
	At higher currents in superconducting coil of K-500 Superconducting cyclotron, it was found that the insulation vacuum surrounding the LHe vessel gets worsen with increased current in the coil,finally leading to slow dump of power of the coil. This is a limitation for further increasing current value in the superconducting magnet coil. But once the current value returned to zero, vacuum reading reaches its initial value. Experiment & analysis have been done to quantify the contribution of molecular gas conduction on heat load because of this partial loss of insulation vacuum. Experiment was done to quantify how much betterment in terms of heat load is possible by incorporating additional vacuum pump. The cryostat safety analysis because of loss of insulation vacuum has become very important at this new scenario. Analysis has been done to know what could be the maximum pressure rise with time in case of loss of vacuum. This data has been used to know what should be the relieving mass flow rate to avoid any pressure burst accident. Finally this data has been compared with the existing relief valve. It is found that the existing safety system can take care of such incident.

Paper

Title

Page

Development of Power Supplies for 3-Ф, 240 kW RF System with Crowbar Protection for Superconducting Cyclotron at VECC

60

S.K. Thakur, R.K. Bhandari, A. De, Y. Kumar, J.S.P. Prasad, S. Saha, S.S. Som, T.P. Tiwari
DAE/VECC, Calcutta, India

RF system of K-500 super conducting cyclotron at VECC is a complex three phase system operating in the frequency range of 9 MHz to 27 MHz with maximum acceleration potential of around 100 kV feeding to each of three Dee cavities placed in median plane of cyclotron 120° apart through coupling capacitors. Each phase consists of chain of amplifiers and resonator operating in synchronization and at final stage of each phase, a high power water cooled Tetrode Tube (Eimac 4CW 150,000 E) as an RF high power amplifier each capable of delivering 80 kW of RF power. Individual power supplies for biasing Anode (20 kV, 22 Amp), Filament (16 V, 225 Amp), Screen (1600 V, 1 Amp) and grid (-500 V, 0.1 Amp) each for all three high power Tetrode Tubes are designed, developed and commissioned indigenously in VECC Cyclotron building and have been in operation from last few months successfully. Anode supply is common to all three tubes, rated at 20 kV, 22 Amp, 450 kW along with fast acting crowbar protection using Ignitron. This paper describes about the technical challenges in the development of the power supplies and special features of protection systems.

MOPCP095

Experiment and Analysis: Partial Loss of Insulation Vacuum in K-500 Superconducting Cyclotron During Energization

248

P. Bhattacharyya, M. Ahammed, S. Bandyopadhyay, R.K. Bhandari, U. Bhunia, J. Chaudhuri, A. De, A. Dutta Gupta, C. Mallik, A. Mukherjee, C. Nandi, U. Panda, S. Saha, S. Saha
DAE/VECC, Calcutta, India

At higher currents in superconducting coil of K-500 Superconducting cyclotron, it was found that the insulation vacuum surrounding the LHe vessel gets worsen with increased current in the coil,finally leading to slow dump of power of the coil. This is a limitation for further increasing current value in the superconducting magnet coil. But once the current value returned to zero, vacuum reading reaches its initial value. Experiment & analysis have been done to quantify the contribution of molecular gas conduction on heat load because of this partial loss of insulation vacuum. Experiment was done to quantify how much betterment in terms of heat load is possible by incorporating additional vacuum pump. The cryostat safety analysis because of loss of insulation vacuum has become very important at this new scenario. Analysis has been done to know what could be the maximum pressure rise with time in case of loss of vacuum. This data has been used to know what should be the relieving mass flow rate to avoid any pressure burst accident. Finally this data has been compared with the existing relief valve. It is found that the existing safety system can take care of such incident.