CYCLOTRONS 2010 - List of Authors (Panda, U.)

Paper	Title	Page
MOPCP008	Control System of Cryogenic Plant for Superconducting Cyclotron at VECC	57
	U. Panda, T. Bhattacharjee, R. Dey, A. Mandal, S. Pal DAE/VECC, Calcutta, India
	Cryogenic Plant of Variable Energy Cyclotron Centre consists of two Helium refrigerators (250 W and 415 W @ 4.5K), valve box with sub-cooler and associated sub systems like pure gas storage, helium purifier and impure gas recovery etc. The system also consists of 3.1K liters of liquid Nitrogen (LN2) storage and delivery system. The plant is designed to cater the cryogenic requirements of the Superconducting Cyclotron. The control system is fully automated and does not require any human intervention once it is started. EPICS architecture has been adopted to design the SCADA module. The EPICS Input Output Controller (IOC) communicates with four Programmable Logic Controllers (PLCs) over Ethernet based control LAN to control/monitor 618 numbers of field inputs/ outputs. The plant is running very reliably round the clock, however, the historical data trending of important parameters during plant operation has been integrated to the system for plant maintenance and easy diagnosis. The 400 kVA UPS with 10 minutes back up time have been installed to keep the cryogenic system running with one 160 kW cycle compressor during utility power interruptions.

MOPCP065	Closed Loop RF Tuning for Superconducitng Cyclotron at VECC	180
	A. Mandal, R.K. Bhandari, S.P. Pal, U. Panda, S. Saha, S. Seth, S.S. Som DAE/VECC, Calcutta, India
	The RF system of Superconducting cyclotron has been operational within 9 - 27 MHz frequency. It has three tunable half-wave coaxial cavities as main resonators and three tunable RF amplifier cavities. A PC-based system takes care of stepper motor driven coarse tuning of cavities with positional accuracy ~20 μm and hydraulically driven three couplers and three trimmers. The couplers, in open loop, match the cavity impedance to 50 Ω in order to feed power from RF amplifier. Trimmers operate in closed loop for fine tuning the cavity, if detuned thermally at high RF power. The control logic has been simulated and finally implemented with Programmable Logic Controller (PLC). Precision control of trimmer (~20 μm) is essential to achieve the accelerating (Dee) voltage stability better than 100 ppm and also minimizing the RF power to maintain it. Phase difference between Dee-in and Dee-pick-off signals and the reflected power signals (from cavity) together act in closed loop for fine tuning of the cavity. The close loop PID control determines the final positioning of the trimmer in each power level and achieved the required voltage stability.

MOPCP076	Operational Experience of Superconducting Cyclotron Magnet at VECC, Kolkata	203
	U. Bhunia, M. Ahmed, R.K. Bhandari, T. Bhattacharyya, M.K. Dey, R. Dey, A. Dutta, A. Dutta Gupta, C. Mallik, C. Nandi, Z.A. Naser, G.P. Pal, U. Panda, S. Paul, J. Pradhan, S. Saha DAE/VECC, Calcutta, India
	The Kolkata Superconducting cyclotron magnet has been operational in the center since last few years and enabled us to extensively map magnetic fields over a year covering the operating range of the machine and successful commissioning of internal beam. The magnet cryostat coupled with the liquid helium refrigerator performs satisfactorily with moderate currents (<550A) in both the coils. The superconducting coil did not undergo any training and over the years has not suffered from any quench. Author would share the experience and difficulties of enhanced overall heat load to the liquid helium refrigerator at higher excitations of coils. This creates instability in the operation of liquid helium refrigerator and finally leads to slow dump. Rigorous study has been carried out in this regard to understand the problems and operational logic of liquid helium refrigerator has been modified accordingly to alleviate from. Some other measures have also been taken from cryostat and cryogenic distribution point of view in order to reduce the heat load at higher excitations.

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

Control System of Cryogenic Plant for Superconducting Cyclotron at VECC

57

U. Panda, T. Bhattacharjee, R. Dey, A. Mandal, S. Pal
DAE/VECC, Calcutta, India

Cryogenic Plant of Variable Energy Cyclotron Centre consists of two Helium refrigerators (250 W and 415 W @ 4.5K), valve box with sub-cooler and associated sub systems like pure gas storage, helium purifier and impure gas recovery etc. The system also consists of 3.1K liters of liquid Nitrogen (LN2) storage and delivery system. The plant is designed to cater the cryogenic requirements of the Superconducting Cyclotron. The control system is fully automated and does not require any human intervention once it is started. EPICS architecture has been adopted to design the SCADA module. The EPICS Input Output Controller (IOC) communicates with four Programmable Logic Controllers (PLCs) over Ethernet based control LAN to control/monitor 618 numbers of field inputs/ outputs. The plant is running very reliably round the clock, however, the historical data trending of important parameters during plant operation has been integrated to the system for plant maintenance and easy diagnosis. The 400 kVA UPS with 10 minutes back up time have been installed to keep the cryogenic system running with one 160 kW cycle compressor during utility power interruptions.

MOPCP065

Closed Loop RF Tuning for Superconducitng Cyclotron at VECC

180

A. Mandal, R.K. Bhandari, S.P. Pal, U. Panda, S. Saha, S. Seth, S.S. Som
DAE/VECC, Calcutta, India

The RF system of Superconducting cyclotron has been operational within 9 - 27 MHz frequency. It has three tunable half-wave coaxial cavities as main resonators and three tunable RF amplifier cavities. A PC-based system takes care of stepper motor driven coarse tuning of cavities with positional accuracy ~20 μm and hydraulically driven three couplers and three trimmers. The couplers, in open loop, match the cavity impedance to 50 Ω in order to feed power from RF amplifier. Trimmers operate in closed loop for fine tuning the cavity, if detuned thermally at high RF power. The control logic has been simulated and finally implemented with Programmable Logic Controller (PLC). Precision control of trimmer (~20 μm) is essential to achieve the accelerating (Dee) voltage stability better than 100 ppm and also minimizing the RF power to maintain it. Phase difference between Dee-in and Dee-pick-off signals and the reflected power signals (from cavity) together act in closed loop for fine tuning of the cavity. The close loop PID control determines the final positioning of the trimmer in each power level and achieved the required voltage stability.

MOPCP076

Operational Experience of Superconducting Cyclotron Magnet at VECC, Kolkata

203

U. Bhunia, M. Ahmed, R.K. Bhandari, T. Bhattacharyya, M.K. Dey, R. Dey, A. Dutta, A. Dutta Gupta, C. Mallik, C. Nandi, Z.A. Naser, G.P. Pal, U. Panda, S. Paul, J. Pradhan, S. Saha
DAE/VECC, Calcutta, India

The Kolkata Superconducting cyclotron magnet has been operational in the center since last few years and enabled us to extensively map magnetic fields over a year covering the operating range of the machine and successful commissioning of internal beam. The magnet cryostat coupled with the liquid helium refrigerator performs satisfactorily with moderate currents (<550A) in both the coils. The superconducting coil did not undergo any training and over the years has not suffered from any quench. Author would share the experience and difficulties of enhanced overall heat load to the liquid helium refrigerator at higher excitations of coils. This creates instability in the operation of liquid helium refrigerator and finally leads to slow dump. Rigorous study has been carried out in this regard to understand the problems and operational logic of liquid helium refrigerator has been modified accordingly to alleviate from. Some other measures have also been taken from cryostat and cryogenic distribution point of view in order to reduce the heat load at higher excitations.

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.