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

Paper	Title	Page
MOPCP041	Beam Tuning in Kolkata Superconducting Cyclotron	132
	M.K. Dey, R.K. Bhandari, U. Bhunia, J. Debnath, A. Dutta, C. Mallik, Z.A. Naser, S. Paul, J. Pradhan, M.H. Rashid DAE/VECC, Calcutta, India
	The Superconducting cyclotron at VECC, Kolkata, has accelerated ion beams up to extraction radius successfully confirmed by the neutrons produced by the nuclear reactions. The internal beam tuning process started with beam parameters calculated using the measured magnetic field data. Due to some mechanical and electrical problems we were forced to tune the beam with three major trim coils off. Accurate positioning of central region Dee-extensions ensuring the proper acceleration gaps in the first turn was required for successful acceleration of beam through the compact central region clearing the posts in the median plane. Here we present different aspects and results of initial beam tuning.

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.

MOPCP078	Study of Magnetic Field Imperfections of Kolkata Superconducting Cyclotron	209
	J. Pradhan, R.K. Bhandari, U. Bhunia, J. Debnath, M.K. Dey, C. Mallik, S. Paul DAE/VECC, Calcutta, India
	Analysis of the magnetic data obtained during the magnetic field mapping of Kolkata superconducting cyclotron showed imperfections in the main magnetic field. Since the main magnet of the superconducting cyclotron is three fold rotationally symmetric, any deviation from this symmetry creates imperfections in the magnetic field. Generally, 1st and 2nd harmonic components are inherently present in the field due to assembling errors in iron/coil. A major portion of these imperfections is attributed to the misplacement/tilting of the iron pole tip with respect to coil. The error in positioning of main superconducting coil with respect to surrounding iron produces another imperfection. Pole tip deformation due to rise of temperature produces field imperfection. This paper reports the various possible sources of imperfection in general and their estimation. The calculation was compared with measured data to find out the actual cause of imperfections and necessary corrections

MOPCP093	Beam Extraction System and External Beam Line of Kolkata Superconducting Cyclotron	242
	J. Debnath, S. Bhattacharya, T. Bhattacharyya, U. Bhunia, P.S. Chakraborty, M.K. Dey, C. Mallik, Z.A. Naser, G.P. Pal, S. Paul, J. Pradhan DAE/VECC, Calcutta, India
	All the major components of the extraction system of the Kolkata superconducting cyclotron are installed and functional. It includes the Electrostatic deflectors, magnetic channels, M9 slit etc. Internal beam acceleration has already been done successfully and now we are on the verge of extracting and transporting the beam to the cave. The external beam transport system has been designed comprising of quadrupole magnets, steering magnets, switching magnets, beam diagnostics etc. One of the four beam lines has been installed, which extends 20 meters up to the experimental cave - 1. Control and monitoring system for all these components have been developed and tested. All the beam dynamical and technical aspects of the beam extraction and beam transportation have been discussed in this paper.

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

Beam Tuning in Kolkata Superconducting Cyclotron

132

M.K. Dey, R.K. Bhandari, U. Bhunia, J. Debnath, A. Dutta, C. Mallik, Z.A. Naser, S. Paul, J. Pradhan, M.H. Rashid
DAE/VECC, Calcutta, India

The Superconducting cyclotron at VECC, Kolkata, has accelerated ion beams up to extraction radius successfully confirmed by the neutrons produced by the nuclear reactions. The internal beam tuning process started with beam parameters calculated using the measured magnetic field data. Due to some mechanical and electrical problems we were forced to tune the beam with three major trim coils off. Accurate positioning of central region Dee-extensions ensuring the proper acceleration gaps in the first turn was required for successful acceleration of beam through the compact central region clearing the posts in the median plane. Here we present different aspects and results of initial beam tuning.

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.

MOPCP078

Study of Magnetic Field Imperfections of Kolkata Superconducting Cyclotron

209

J. Pradhan, R.K. Bhandari, U. Bhunia, J. Debnath, M.K. Dey, C. Mallik, S. Paul
DAE/VECC, Calcutta, India

Analysis of the magnetic data obtained during the magnetic field mapping of Kolkata superconducting cyclotron showed imperfections in the main magnetic field. Since the main magnet of the superconducting cyclotron is three fold rotationally symmetric, any deviation from this symmetry creates imperfections in the magnetic field. Generally, 1st and 2nd harmonic components are inherently present in the field due to assembling errors in iron/coil. A major portion of these imperfections is attributed to the misplacement/tilting of the iron pole tip with respect to coil. The error in positioning of main superconducting coil with respect to surrounding iron produces another imperfection. Pole tip deformation due to rise of temperature produces field imperfection. This paper reports the various possible sources of imperfection in general and their estimation. The calculation was compared with measured data to find out the actual cause of imperfections and necessary corrections

MOPCP093

Beam Extraction System and External Beam Line of Kolkata Superconducting Cyclotron

242

J. Debnath, S. Bhattacharya, T. Bhattacharyya, U. Bhunia, P.S. Chakraborty, M.K. Dey, C. Mallik, Z.A. Naser, G.P. Pal, S. Paul, J. Pradhan
DAE/VECC, Calcutta, India

All the major components of the extraction system of the Kolkata superconducting cyclotron are installed and functional. It includes the Electrostatic deflectors, magnetic channels, M9 slit etc. Internal beam acceleration has already been done successfully and now we are on the verge of extracting and transporting the beam to the cave. The external beam transport system has been designed comprising of quadrupole magnets, steering magnets, switching magnets, beam diagnostics etc. One of the four beam lines has been installed, which extends 20 meters up to the experimental cave - 1. Control and monitoring system for all these components have been developed and tested. All the beam dynamical and technical aspects of the beam extraction and beam transportation have been discussed in this paper.

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.