deepak raparia | Brookhaven National Laboratory (original) (raw)

Papers by deepak raparia

Proceedings of the 2005 Particle Accelerator Conference, Feb 15, 2006

The diamond stripper foils in use at the Spallation Neutron Source worked successfully with no fa... more The diamond stripper foils in use at the Spallation Neutron Source worked successfully with no failures until May 3, 2009, when we started experiencing a rash of foil failures after increasing the beam power to ~840 kW. The main contributions to foil failure are thought to be 1) convoy electrons, stripped from the incoming H− beam, that strike the foil bracket and may also reflect back from the electron catcher, and 2) vacuum breakdown from the charge developed on the foil by secondary electron emission. In this paper we will detail these and other failure mechanisms, and describe the improvements we have made to mitigate them.

The Review of scientific instruments, 2016

Electron diode guns, which have strongly varying magnetic or electric fields in a cathode-anode g... more Electron diode guns, which have strongly varying magnetic or electric fields in a cathode-anode gap, were investigated in order to generate laminar electron beams with high current density using magnetically immersed guns. By creating a strongly varying radial electric field in a cathode-anode gap of the electron gun, it was demonstrated that the optical properties of the gun can be significantly altered, which allows the generation of a laminar, high-current electron beam with relatively low magnetic field on the cathode. The relatively high magnetic compression of the electron beam achieved by this method is important for producing electron beams with high current density. A similar result can be obtained by inducing a strong variation of the magnetic field in a cathode-anode gap. It was observed that creating a dip in the axial magnetic field in the cathode-anode gap of an adiabatic electron gun has an optical effect similar to guns with strong variation of radial electric field....

AIP Conference Proceedings, 2003

ABSTRACT The collimating system in the accumulator ring and transfer lines of the Spallation Neut... more ABSTRACT The collimating system in the accumulator ring and transfer lines of the Spallation Neutron Source (SNS) project is responsible for stopping 0.1% of the 2 MW beam of 1.0 GeV protons that are in the beam halo. The collimating structures are a combination of movable beam scrapers and stationary absorbers. Specifically, pairs of charge‐exchange foils or scrapers moving in‐and‐out of the beam in the vertical and horizontal directions help guide the halo protons into respective absorbers which consist of an intricate design of a double wall beam tube, a water‐cooled particle bed and radial shielding. Off‐momentum protons, with the help of respective charge exchange foils and a dipole magnet, are directed to a momentum dump consisting of a cooled particle bed downstream of a double‐walled window separating it from the vacuum space. Addressed in this paper is the thermo‐mechanical response and survivability of key components of the collimating system (such as the collimating beam tube in the absorbers, the beam windows and the primary element of the bean scraper structure) in the event of intercept of the full beam under accident conditions. While the potential for the full beam to be intercepted by these components is remote, still special attention will be paid in assessing the amount of full beam (or number of pulses) they can tolerate. © 2003 American Institute of Physics

AIP Conference Proceedings, 2003

ABSTRACT The performance of the RHIC Optically-Pumped Polarized H- Ion Source (OPPIS) in 2000-200... more ABSTRACT The performance of the RHIC Optically-Pumped Polarized H- Ion Source (OPPIS) in 2000-2002 runs in AGS and RHIC is reviewed. The OPPIS met the RHIC requirements for beam intensity with the reliable delivery of about 500 muA polarized H- ion current in 400 mus pulse duration (current can be increased to over 1.0 mA, if necessary). The beam intensity at 200 MeV was (5-6) 1011 H-/pulse, which is sufficient to obtain the required 2.1011 polarized protons per bunch in RHIC. The polarization dilution by molecular ions, which are produced in the ECR primary proton source is discussed. The molecular component can be reduced to about 5% by further ECR source-operation optimization. The molecular component is suppressed by optimization of the extraction electrode optics and by the decelerating einzel lens in the 35 keV LEBT line. As a result, the proton polarization of the accelerated beam was increased to over 80%, as measured in the 200 MeV proton-deuterium polarimeter.

The Spallation Neutron Source comprises a 1 GeV, 1.4 MW linear accelerator followed by an accumul... more The Spallation Neutron Source comprises a 1 GeV, 1.4 MW linear accelerator followed by an accumulator ring and a liquid mercury target. To manage the beam loss caused by the H0H^0H0 excited states created during the H−H^-H− charge exchange injection into the accumulator ring, the stripper foil is located inside one of the chicane dipoles. This has some interesting consequences that were not fully appreciated until the beam power reached about 840 kW. One consequence was sudden failure of the stripper foil system due to convoy electrons stripped from the incoming H−H^-H− beam, which circled around to strike the foil bracket and cause bracket failure. Another consequence is that convoy electrons can reflect back up from the electron catcher and strike the foil and bracket. An additional contributor to foil system failure is vacuum breakdown due to the charge developed on the foil by secondary electron emission. In this paper we detail these and other interesting failure mechanisms and descr...

2013 IEEE SENSORS, 2013

ABSTRACT Electrodynamically driven resonators upon immersion in a sample liquid which can be used... more ABSTRACT Electrodynamically driven resonators upon immersion in a sample liquid which can be used as viscosity and mass density sensors are presented. The most promising concepts for such resonant sensors include devices which are fabricated in technologies involving clamped wire and plate structures. In this contribution, achievable accuracies for these types of resonating sensors are considered and investigated by means of long term measurement series. As a suitable reference for such devices, a steel tuning fork is used, which serves as a frequency standard in low frequency applications (440 Hz). Such tuning forks can serve as viscosity and density sensors themselves if they are immersed in a liquid. In order to make their frequency response electronically accessible, an electromagnetic driving and readout setup has been devised to compare their performance to the wire-and plate-based sensors.

The BNL 200 MeV linac presently provides beam for the AGS high energy physics program and for iso... more The BNL 200 MeV linac presently provides beam for the AGS high energy physics program and for isotope production at the Brookhaven Linac Isotope Producer (BLIP,) facility. There is now a proposal to develop a proton therapy facility which would also use the linac beam. Approximately 1% of the current in each linac beam pulse would be diverted from BLIP,

Review of Scientific Instruments, 2002

A new optically pumped polarized H− ion source (OPPIS) was developed for the RHIC polarization pr... more A new optically pumped polarized H− ion source (OPPIS) was developed for the RHIC polarization program and successfully used for the first polarized beam commissioning at RHIC. The OPPIS produces in excess of 1.0 mA H− ion current at about 80% polarization. An ECR primary proton source development and a new 29 GHz microwave power supply are described. A new type sodium-jet ionizer cell is biased to −32 kV to produce a 35 keV polarized beam ready for injection to the RFQ. Higher current and higher polarization were also obtained with the biased jet-cell in comparison with an old oven-type ionizer cell.

Physical Review Special Topics - Accelerators and Beams, 2005

One of the main sources of electrons in the Spallation Neutron Source's Accumulator Ring is the s... more One of the main sources of electrons in the Spallation Neutron Source's Accumulator Ring is the stripped electrons in the injection region. A magnetic field guides the stripped electrons to the bottom of the beam pipe, where an electron catcher with overhanging surface traps them. This paper describes the stripped electrons' motion, the optimization of the catcher, and the build up of an electron cloud in this region.

Citeseer

... Brookhaven National Laboratory Box 5000, Upton, NY 11973-5000 W. Frati, JR Klein, K. Lande, A... more ... Brookhaven National Laboratory Box 5000, Upton, NY 11973-5000 W. Frati, JR Klein, K. Lande, AK Mann, R. Van Berg and P. Wildenhain University of Pennsylvania Philadelphia, PA 19104-6396 R. Corey South Dakota School of Mines and Technology Rapid City, SD 57701 ...

IEEE Transactions on Nuclear Science, 1985

For the TRIUMF KAON Factory a 450 MeV Accumulator ring is required to match the cw 100 pA beam fr... more For the TRIUMF KAON Factory a 450 MeV Accumulator ring is required to match the cw 100 pA beam from the isochronous cyclotron to the first acceleration stage, a 50 Hz 3 GeV Booster Synchrotron. H-ions would be charge exchange injected into the Accumulator through a 250 p g cm-2 carbon foil. Approximately 2 A of protons would be accumulated over the 20 ms Booster period and transferred to the Booster in one turn. The first protons injected circulate for about 2x104 turns before extraction. If a substantial fraction of the circulating protons traverse the foil each turn, both the lifetime of the foil and the amount of beam lost would be unacceptable. The proposed acceptances of the Accumulator are 100 ir pm horizontally, 30 Xt pm vertically and 7.6x10-2 eV-s longitudinally. These are much larger than the TRIUMF emittances of 2 i mmmrad in each transverse plane and 10-3 eV-s longitudinally. It is shown that with simultaneous stacking in the transverse and longitudinal acceptances it is possible to reduce the number of foil traversals per proton to an acceptable number 100.

12th International Conference on Nuclear Engineering, Volume 2, 2004

This paper details the integration scheme as well as the induced activation by the proton beam cl... more This paper details the integration scheme as well as the induced activation by the proton beam clean-up system (collimation) in the accumulator ring section of the Spallation Neutron Source (SNS) accelerator complex. Specifically, the results of the optimization study in terms of satisfying both the optics of the proton beam and the minimization of activation of the accelerator components as well as of the surrounding structure have guided both the design of the components and their integration and are presented in this paper. The resulted collimation scheme is a two-stage clean-up system consisting of proton beam halo intercepting scrapers and appropriate fixed aperture absorbers. The accumulator ring structure consists of the High Energy Beam Transfer (HEBT) line which receives the 1 GeV proton beam from the SNS LINAC accelerator, the accumulator ring itself which compiles the micro-pulses into the final 60 Hz pulse, and the RTBT line that transfers the final proton pulse to the a...

Soryushiron Kenkyu Electronics, 2001

The Spallation Neutron Source (SNS) accumulator ring is a high intensity ring and must have low u... more The Spallation Neutron Source (SNS) accumulator ring is a high intensity ring and must have low uncontrolled losses for hands on maintenance. To achieve these low losses one needs very tight tolerance. These tight tolerances have been achieved through shimming the magnets and sorting. Dipoles are solid core magnets and had very good field quality but magnet to magnet variation were sorted out according to ITF, since all the dipole are powered with one power supply. Typically, sorting is done to minimize linear effects in beam dynamics. Here, sorting of quadrupoles was done according to a scheme, which allows reducing unwanted strength of nonlinear resonances. As a result, the strength of sextupole resonances for our base line tune-box was strongly reduced which was confirmed by a subsequent beam dynamics simulation.

The mechanism of electron multipacting in long bunched proton machine has been quantitatively des... more The mechanism of electron multipacting in long bunched proton machine has been quantitatively described by the electron energy gain and electron motion. Some important parameters related to electron multipacting are investigated in detail. It is proved that multipacting is sensitive to beam intensity, longitudinal beam profile shape and transverse beam size. Agreements are achieved among our analysis, simulation and experiment. The possible remedies to clearing electron cloud are also investigated.

Review of Scientific Instruments, 2020

We are proposing a compact neutron generator based on a Li beam driver. The proposed neutron gene... more We are proposing a compact neutron generator based on a Li beam driver. The proposed neutron generator comprises a laser ion source, a radio-frequency quadrupole linear accelerator (RFQ linac), a drift tube linac, and a target containing protons. In the generator, the lithium ion is used as a projectile instead of protons to utilize the kinematic focusing technique. The technique enables us to enhance the neutron flux without increasing the beam energy, which is important to develop a clean compact neutron generator. Moreover, the combination of a laser ion source and a RFQ linac with the direct plasma injection scheme will provide several tens of mA of a fully ionized lithium beam, which is much higher than that of conventional heavy ion sources comparable with proton drivers. Neutrons are generated by the nuclear reaction of the lithium ions and protons in the beam target. In this paper, we reported the current status of the development. For RFQ, we designed the RFQ rods to accele...

Proceedings of the 2005 Particle Accelerator Conference, Feb 15, 2006

The diamond stripper foils in use at the Spallation Neutron Source worked successfully with no fa... more The diamond stripper foils in use at the Spallation Neutron Source worked successfully with no failures until May 3, 2009, when we started experiencing a rash of foil failures after increasing the beam power to ~840 kW. The main contributions to foil failure are thought to be 1) convoy electrons, stripped from the incoming H− beam, that strike the foil bracket and may also reflect back from the electron catcher, and 2) vacuum breakdown from the charge developed on the foil by secondary electron emission. In this paper we will detail these and other failure mechanisms, and describe the improvements we have made to mitigate them.

The Review of scientific instruments, 2016

Electron diode guns, which have strongly varying magnetic or electric fields in a cathode-anode g... more Electron diode guns, which have strongly varying magnetic or electric fields in a cathode-anode gap, were investigated in order to generate laminar electron beams with high current density using magnetically immersed guns. By creating a strongly varying radial electric field in a cathode-anode gap of the electron gun, it was demonstrated that the optical properties of the gun can be significantly altered, which allows the generation of a laminar, high-current electron beam with relatively low magnetic field on the cathode. The relatively high magnetic compression of the electron beam achieved by this method is important for producing electron beams with high current density. A similar result can be obtained by inducing a strong variation of the magnetic field in a cathode-anode gap. It was observed that creating a dip in the axial magnetic field in the cathode-anode gap of an adiabatic electron gun has an optical effect similar to guns with strong variation of radial electric field....

AIP Conference Proceedings, 2003

ABSTRACT The collimating system in the accumulator ring and transfer lines of the Spallation Neut... more ABSTRACT The collimating system in the accumulator ring and transfer lines of the Spallation Neutron Source (SNS) project is responsible for stopping 0.1% of the 2 MW beam of 1.0 GeV protons that are in the beam halo. The collimating structures are a combination of movable beam scrapers and stationary absorbers. Specifically, pairs of charge‐exchange foils or scrapers moving in‐and‐out of the beam in the vertical and horizontal directions help guide the halo protons into respective absorbers which consist of an intricate design of a double wall beam tube, a water‐cooled particle bed and radial shielding. Off‐momentum protons, with the help of respective charge exchange foils and a dipole magnet, are directed to a momentum dump consisting of a cooled particle bed downstream of a double‐walled window separating it from the vacuum space. Addressed in this paper is the thermo‐mechanical response and survivability of key components of the collimating system (such as the collimating beam tube in the absorbers, the beam windows and the primary element of the bean scraper structure) in the event of intercept of the full beam under accident conditions. While the potential for the full beam to be intercepted by these components is remote, still special attention will be paid in assessing the amount of full beam (or number of pulses) they can tolerate. © 2003 American Institute of Physics

AIP Conference Proceedings, 2003

ABSTRACT The performance of the RHIC Optically-Pumped Polarized H- Ion Source (OPPIS) in 2000-200... more ABSTRACT The performance of the RHIC Optically-Pumped Polarized H- Ion Source (OPPIS) in 2000-2002 runs in AGS and RHIC is reviewed. The OPPIS met the RHIC requirements for beam intensity with the reliable delivery of about 500 muA polarized H- ion current in 400 mus pulse duration (current can be increased to over 1.0 mA, if necessary). The beam intensity at 200 MeV was (5-6) 1011 H-/pulse, which is sufficient to obtain the required 2.1011 polarized protons per bunch in RHIC. The polarization dilution by molecular ions, which are produced in the ECR primary proton source is discussed. The molecular component can be reduced to about 5% by further ECR source-operation optimization. The molecular component is suppressed by optimization of the extraction electrode optics and by the decelerating einzel lens in the 35 keV LEBT line. As a result, the proton polarization of the accelerated beam was increased to over 80%, as measured in the 200 MeV proton-deuterium polarimeter.

The Spallation Neutron Source comprises a 1 GeV, 1.4 MW linear accelerator followed by an accumul... more The Spallation Neutron Source comprises a 1 GeV, 1.4 MW linear accelerator followed by an accumulator ring and a liquid mercury target. To manage the beam loss caused by the H0H^0H0 excited states created during the H−H^-H− charge exchange injection into the accumulator ring, the stripper foil is located inside one of the chicane dipoles. This has some interesting consequences that were not fully appreciated until the beam power reached about 840 kW. One consequence was sudden failure of the stripper foil system due to convoy electrons stripped from the incoming H−H^-H− beam, which circled around to strike the foil bracket and cause bracket failure. Another consequence is that convoy electrons can reflect back up from the electron catcher and strike the foil and bracket. An additional contributor to foil system failure is vacuum breakdown due to the charge developed on the foil by secondary electron emission. In this paper we detail these and other interesting failure mechanisms and descr...

2013 IEEE SENSORS, 2013

ABSTRACT Electrodynamically driven resonators upon immersion in a sample liquid which can be used... more ABSTRACT Electrodynamically driven resonators upon immersion in a sample liquid which can be used as viscosity and mass density sensors are presented. The most promising concepts for such resonant sensors include devices which are fabricated in technologies involving clamped wire and plate structures. In this contribution, achievable accuracies for these types of resonating sensors are considered and investigated by means of long term measurement series. As a suitable reference for such devices, a steel tuning fork is used, which serves as a frequency standard in low frequency applications (440 Hz). Such tuning forks can serve as viscosity and density sensors themselves if they are immersed in a liquid. In order to make their frequency response electronically accessible, an electromagnetic driving and readout setup has been devised to compare their performance to the wire-and plate-based sensors.

The BNL 200 MeV linac presently provides beam for the AGS high energy physics program and for iso... more The BNL 200 MeV linac presently provides beam for the AGS high energy physics program and for isotope production at the Brookhaven Linac Isotope Producer (BLIP,) facility. There is now a proposal to develop a proton therapy facility which would also use the linac beam. Approximately 1% of the current in each linac beam pulse would be diverted from BLIP,

Review of Scientific Instruments, 2002

A new optically pumped polarized H− ion source (OPPIS) was developed for the RHIC polarization pr... more A new optically pumped polarized H− ion source (OPPIS) was developed for the RHIC polarization program and successfully used for the first polarized beam commissioning at RHIC. The OPPIS produces in excess of 1.0 mA H− ion current at about 80% polarization. An ECR primary proton source development and a new 29 GHz microwave power supply are described. A new type sodium-jet ionizer cell is biased to −32 kV to produce a 35 keV polarized beam ready for injection to the RFQ. Higher current and higher polarization were also obtained with the biased jet-cell in comparison with an old oven-type ionizer cell.

Physical Review Special Topics - Accelerators and Beams, 2005

One of the main sources of electrons in the Spallation Neutron Source's Accumulator Ring is the s... more One of the main sources of electrons in the Spallation Neutron Source's Accumulator Ring is the stripped electrons in the injection region. A magnetic field guides the stripped electrons to the bottom of the beam pipe, where an electron catcher with overhanging surface traps them. This paper describes the stripped electrons' motion, the optimization of the catcher, and the build up of an electron cloud in this region.

Citeseer

... Brookhaven National Laboratory Box 5000, Upton, NY 11973-5000 W. Frati, JR Klein, K. Lande, A... more ... Brookhaven National Laboratory Box 5000, Upton, NY 11973-5000 W. Frati, JR Klein, K. Lande, AK Mann, R. Van Berg and P. Wildenhain University of Pennsylvania Philadelphia, PA 19104-6396 R. Corey South Dakota School of Mines and Technology Rapid City, SD 57701 ...

IEEE Transactions on Nuclear Science, 1985

For the TRIUMF KAON Factory a 450 MeV Accumulator ring is required to match the cw 100 pA beam fr... more For the TRIUMF KAON Factory a 450 MeV Accumulator ring is required to match the cw 100 pA beam from the isochronous cyclotron to the first acceleration stage, a 50 Hz 3 GeV Booster Synchrotron. H-ions would be charge exchange injected into the Accumulator through a 250 p g cm-2 carbon foil. Approximately 2 A of protons would be accumulated over the 20 ms Booster period and transferred to the Booster in one turn. The first protons injected circulate for about 2x104 turns before extraction. If a substantial fraction of the circulating protons traverse the foil each turn, both the lifetime of the foil and the amount of beam lost would be unacceptable. The proposed acceptances of the Accumulator are 100 ir pm horizontally, 30 Xt pm vertically and 7.6x10-2 eV-s longitudinally. These are much larger than the TRIUMF emittances of 2 i mmmrad in each transverse plane and 10-3 eV-s longitudinally. It is shown that with simultaneous stacking in the transverse and longitudinal acceptances it is possible to reduce the number of foil traversals per proton to an acceptable number 100.

12th International Conference on Nuclear Engineering, Volume 2, 2004

This paper details the integration scheme as well as the induced activation by the proton beam cl... more This paper details the integration scheme as well as the induced activation by the proton beam clean-up system (collimation) in the accumulator ring section of the Spallation Neutron Source (SNS) accelerator complex. Specifically, the results of the optimization study in terms of satisfying both the optics of the proton beam and the minimization of activation of the accelerator components as well as of the surrounding structure have guided both the design of the components and their integration and are presented in this paper. The resulted collimation scheme is a two-stage clean-up system consisting of proton beam halo intercepting scrapers and appropriate fixed aperture absorbers. The accumulator ring structure consists of the High Energy Beam Transfer (HEBT) line which receives the 1 GeV proton beam from the SNS LINAC accelerator, the accumulator ring itself which compiles the micro-pulses into the final 60 Hz pulse, and the RTBT line that transfers the final proton pulse to the a...

Soryushiron Kenkyu Electronics, 2001

The Spallation Neutron Source (SNS) accumulator ring is a high intensity ring and must have low u... more The Spallation Neutron Source (SNS) accumulator ring is a high intensity ring and must have low uncontrolled losses for hands on maintenance. To achieve these low losses one needs very tight tolerance. These tight tolerances have been achieved through shimming the magnets and sorting. Dipoles are solid core magnets and had very good field quality but magnet to magnet variation were sorted out according to ITF, since all the dipole are powered with one power supply. Typically, sorting is done to minimize linear effects in beam dynamics. Here, sorting of quadrupoles was done according to a scheme, which allows reducing unwanted strength of nonlinear resonances. As a result, the strength of sextupole resonances for our base line tune-box was strongly reduced which was confirmed by a subsequent beam dynamics simulation.

The mechanism of electron multipacting in long bunched proton machine has been quantitatively des... more The mechanism of electron multipacting in long bunched proton machine has been quantitatively described by the electron energy gain and electron motion. Some important parameters related to electron multipacting are investigated in detail. It is proved that multipacting is sensitive to beam intensity, longitudinal beam profile shape and transverse beam size. Agreements are achieved among our analysis, simulation and experiment. The possible remedies to clearing electron cloud are also investigated.

Review of Scientific Instruments, 2020

We are proposing a compact neutron generator based on a Li beam driver. The proposed neutron gene... more We are proposing a compact neutron generator based on a Li beam driver. The proposed neutron generator comprises a laser ion source, a radio-frequency quadrupole linear accelerator (RFQ linac), a drift tube linac, and a target containing protons. In the generator, the lithium ion is used as a projectile instead of protons to utilize the kinematic focusing technique. The technique enables us to enhance the neutron flux without increasing the beam energy, which is important to develop a clean compact neutron generator. Moreover, the combination of a laser ion source and a RFQ linac with the direct plasma injection scheme will provide several tens of mA of a fully ionized lithium beam, which is much higher than that of conventional heavy ion sources comparable with proton drivers. Neutrons are generated by the nuclear reaction of the lithium ions and protons in the beam target. In this paper, we reported the current status of the development. For RFQ, we designed the RFQ rods to accele...