IPAC2013 - List of Authors (Li, D.)

Paper

Title

Page

Project X Injector Experiment: Goals, Plan and Status

1093

A.V. Shemyakin, S.D. Holmes, D.E. Johnson, M. Kaducak, R.D. Kephart, V.A. Lebedev, C.S. Mishra, S. Nagaitsev, N. Solyak, R.P. Stanek, V.P. Yakovlev
Fermilab, Batavia, USA
D. Li
LBNL, Berkeley, California, USA
P.N. Ostroumov
ANL, Argonne, USA

Funding: This work was supported by the U.S. DOE under Contract No.DE-AC02-07CH11359
A multi-MW proton facility, Project X, has been proposed and is currently under development at Fermilab. We are carrying out a program of research and development aimed at integrated systems testing of critical components comprising the front end of the Project X. This program is being undertaken as a key component of the larger Project X R&D program. The successful completion of this program will validate the concept for the Project X front end, thereby minimizing a primary technical risk element within Project X. Integrated systems testing, known as the Project X Injector Experiment (PXIE), will be accomplished with a new test facility under construction at Fermilab and will be completed over the period FY12- 17. PXIE will include an H⁻ ion source, a CW 2.1-MeV RFQ and two superconductive RF (SRF) cryomodules providing up to 25 MeV energy gain at an average beam current of 1 mA (upgradable to 2 mA). Successful systems testing will also demonstrate the viability of novel front end technologies that are expected find applications beyond Project X.

Slides TUOAB102 [1.615 MB]

WEPWA070

Design of a Collimation System for the Next Generation Light Source

2277

C. Steier, J.M. Byrd, S. De Santis, P. Emma, D. Li, H. Nishimura, C. F. Papadopoulos, H.J. Qian, F. Sannibale
LBNL, Berkeley, California, USA

Funding: This work is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The Next Generation Light Source at LBNL will deliver MHz repetition rate electron beams to an array of free electron lasers. Because of the high beam power approaching one MW in such a facility, effective beam collimation is extremely important to minimize radiation damage, prevent quenches of superconducting cavities, limit dose rates outside of the accelerator tunnel and prevent equipment damage. This paper describes the conceptual design of a collimation system, including detailed simulations to verify its effectiveness.

WEPFI066

The RF System for the MICE Experiment

2848

K. Ronald, A.J. Dick, C.G. Whyte
USTRAT/SUPA, Glasgow, United Kingdom
P.A. Corlett
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
A.J. DeMello, D. Li, S.P. Virostek
LBNL, Berkeley, California, USA
A.F. Grant, A.J. Moss, C.J. White
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
P.M. Hanlet
IIT, Chicago, Illinois, USA
C. Hunt, K.R. Long, J. Pasternak
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
T.H. Luo, D.J. Summers
UMiss, University, Mississippi, USA
A. Moretti, R.J. Pasquinelli, D.W. Peterson, R.P. Schultz, J.T. Volk
Fermilab, Batavia, USA
P.J. Smith
Sheffield University, Sheffield, United Kingdom
T. Stanley
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
Y. Torun
Illinois Institute of Technology, Chicago, IL, USA

The International Muon Ionisation Cooling Experiment (MICE) is designed to demonstrate the effectiveness of ionisation cooling to reduce the phase space footprint of a muon beam, principally to allow the subsequent acceleration of muons for next generation colliders and/or neutrino factories. The experiment (and indeed any subsequent accelerator cooling channel based on the same principles) poses certain unusual requirements on its RF system, whilst the precision measurement of the ionisation cooling process demands special diagnostics. This paper shall outline the key features of the RF system, including the LLRF control, the power amplifier chain, distribution network, cavities, tuners and couplers, all of which must operate in a high magnetic field environment. The RF diagnostics which, in conjunction with the other MICE diagnostics, shall allow detailed knowledge of the amplitude and phase of the acceleration field during the transit of each individual Muon shall also be outlined.

WEPFI072

Analysis of Breakdown Damage in an 805 MHz Pillbox Cavity for Muon Ionization Cooling R&D

2857

D.L. Bowring, D. Li
LBNL, Berkeley, California, USA
A. Moretti, Y. Torun
Fermilab, Batavia, USA

When operating in multi-Tesla solenoidal magnetic fields, normal-conducting cavities exhibit RF breakdown at anomalously low gradients. This breakdown behavior may be due to field-emitted electrons, focused by the magnetic field into "beamlets" with relatively large current densities. These beamlets may then cause pulsed heating and cyclic fatigue damage on cavity interior surfaces. If this model is correct, materials with long radiation lengths (relative to copper) may alleviate the problem of RF breakdown in strong magnetic fields. To study this phenomenon, RF breakdown was induced on pairs of "buttons" in an 805 MHz pillbox cavity. The shape of the buttons creates a local enhancement of the surface electric field, such that breakdown occurs preferentially on the button surface. Beryllium and copper buttons were tested in order to evaluate the effect of radiation length on RF breakdown performance. This poster presents an analysis of the damage to these buttons and suggests a path forward for future materials R&D related to breakdown in strong magnetic fields.

WEPFI073

A Modular Cavity for Muon Ionization Cooling R&D

2860

D.L. Bowring, A.J. DeMello, A.R. Lambert, D. Li, S.P. Virostek, M.S. Zisman
LBNL, Berkeley, California, USA
C. Adolphsen, L. Ge, A.A. Haase, K.H. Lee, Z. Li, D.W. Martin
SLAC, Menlo Park, California, USA
D.M. Kaplan
Illinois Institute of Technology, Chicago, Illinois, USA
T.H. Luo, D.J. Summers
UMiss, University, Mississippi, USA
A. Moretti, M.A. Palmer, R.J. Pasquinelli, Y. Torun
Fermilab, Batavia, USA
R.B. Palmer
BNL, Upton, Long Island, New York, USA

The Muon Accelerator Program (MAP) collaboration is developing an ionization cooling channel for muon beams. Ionization cooling channel designs call for the operation of high-gradient, normal-conducting RF cavities in multi-Tesla solenoidal magnetic fields. However, strong magnetic fields have been shown to limit the maximum achievable gradient in RF cavities. This gradient limit is characterized by RF breakdown and damage to the cavity surface. To study this issue, we have developed an experimental program based on a modular pillbox cavity operating at 805 MHz. The modular cavity design allows for the evaluation of different cavity materials - such as beryllium - which may ameliorate or circumvent RF breakdown triggers. Modular cavity components may furthermore be prepared with different surface treatments, such as high-temperature baking or chemical polishing. This poster presents the design and experimental status of the modular cavity, as well as future plans for the experimental program.

WEPFI091

Design of a Normal-conducting RF-dipole Deflecting Cavity

2911

T.H. Luo, D.J. Summers
UMiss, University, Mississippi, USA
D. Li
LBNL, Berkeley, California, USA

In this paper we present a novel design of a CW normal conducting RF deflecting cavity. The cavity is designed into a dipole-like structure, resulting a high (R/Q)_transverse. The geometry at high H field is optimized to lower the surface peak power. We will show the design of a 325 MHz and 163 MHz cavity based on this structure and compare their performances with their superconducting counterparts.

WEPFI092

Multipacting Simulation of the MICE 201 MHz RF Cavity

2914

T.H. Luo, D.J. Summers
UMiss, University, Mississippi, USA
D.L. Bowring, A.J. DeMello, D. Li, P. Pan, S.P. Virostek
LBNL, Berkeley, California, USA
L. Ge
SLAC, Menlo Park, California, USA

The international Muon Ionization Cooling Experiment (MICE) aims to demonstrate transverse cooling of muon beams by ionization. The MICE ionization cooling channel requires eight 201-MHz normal conducting RF cavities to compensate for the longitudinal beam energy loss in the cooling channel. Multipacting is a resonant electron discharge produced by the synchronization of emitted electrons with the RF fields, which can cause breakdown at high power RF operation. In this paper, we present the study of the multipacting effect in the MICE 201 MHz cavities with the SLAC ACE3P code. The simulation is carried out in the cavity body, the RF coupler region, and the coaxial waveguide, with the external magnetic field from the Coupling Coil. We will identify potential RF breakdowns due to multipacting and propose a solution to suppress them.

THPME047

Progress of the RFQ Accelerator for PXIE

3618

D. Li, M.D. Hoff, A.R. Lambert, J.W. Staples, S.P. Virostek
LBNL, Berkeley, California, USA
T.H. Luo
UMiss, University, Mississippi, USA
S. Nagaitsev, G.V. Romanov, A.V. Shemyakin, R.P. Stanek, J. Steimel
Fermilab, Batavia, USA

Funding: This work is supported by the Office of Science, United States Department of Energy under DOE contract DE-AC02-05CH11231.
The proposed Project X Injector Experiment (PXIE) is currently under development at Fermilab. PXIE is an R&D test accelerator that will replicate the front-end portion of Project X. The PXIE accelerator complex consists of a H⁻ ion source(s), low-energy beam transport (LEBT), 162.5 MHz normal conducting CW Radio-Frequency-Quadrupole (RFQ) accelerator, medium-energy beam transport (MEBT), broad-band beam chopper(s) and two superconducting cryomodules. In this paper, we will review and present recent progress of the PXIE RFQ, which will include an overview of the RFQ beam dynamics design, RF structure design, detailed thermal and mechanical analyses, fabrication test results and fabrication plan and schedule.

THPME048

Assembly and Test of a Modified Spectrometer Solenoid for MICE

3621

S.P. Virostek, D. Li, P. Pan, S. Prestemon
LBNL, Berkeley, California, USA
R. Preece
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom

Funding: This work is supported by the Office of Science, US-DOE under DOE contract DE-AC02-05CH11231.
The MICE superconducting spectrometer solenoids have been modified and rebuilt as a result of the testing done in 2008, 2009 and 2010. The number of two-stage cryocoolers was increased from three in 2009 to five in the modified magnet. The new shield for the spectrometer solenoid is fabricated primarily from 1100-O aluminum instead of 6061-T6 aluminum used in the former versions of the magnet. The thermal connection between the shield and the first-stage of the cold heads has been improved to reduce the temperature drop between the shield and the coolers. As a result of these changes, the first-stage temperatures for the coolers are below 45K, which resulted in an increase in the refrigeration generated by the cooler second stages. The quench protection system has been altered in order to provide additional protection to the magnet in the event of a lead failure between the magnet power supply and the magnet coils. The quality of the shield and cold mass MLI wrap has also been improved. Details of the modifications and test results demonstrating improved magnet performance are presented in this paper.

Paper	Title	Page
TUOAB102	Project X Injector Experiment: Goals, Plan and Status	1093
	A.V. Shemyakin, S.D. Holmes, D.E. Johnson, M. Kaducak, R.D. Kephart, V.A. Lebedev, C.S. Mishra, S. Nagaitsev, N. Solyak, R.P. Stanek, V.P. Yakovlev Fermilab, Batavia, USA D. Li LBNL, Berkeley, California, USA P.N. Ostroumov ANL, Argonne, USA
	Funding: This work was supported by the U.S. DOE under Contract No.DE-AC02-07CH11359 A multi-MW proton facility, Project X, has been proposed and is currently under development at Fermilab. We are carrying out a program of research and development aimed at integrated systems testing of critical components comprising the front end of the Project X. This program is being undertaken as a key component of the larger Project X R&D program. The successful completion of this program will validate the concept for the Project X front end, thereby minimizing a primary technical risk element within Project X. Integrated systems testing, known as the Project X Injector Experiment (PXIE), will be accomplished with a new test facility under construction at Fermilab and will be completed over the period FY12- 17. PXIE will include an H⁻ ion source, a CW 2.1-MeV RFQ and two superconductive RF (SRF) cryomodules providing up to 25 MeV energy gain at an average beam current of 1 mA (upgradable to 2 mA). Successful systems testing will also demonstrate the viability of novel front end technologies that are expected find applications beyond Project X.
	Slides TUOAB102 [1.615 MB]

WEPWA070	Design of a Collimation System for the Next Generation Light Source	2277
	C. Steier, J.M. Byrd, S. De Santis, P. Emma, D. Li, H. Nishimura, C. F. Papadopoulos, H.J. Qian, F. Sannibale LBNL, Berkeley, California, USA
	Funding: This work is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The Next Generation Light Source at LBNL will deliver MHz repetition rate electron beams to an array of free electron lasers. Because of the high beam power approaching one MW in such a facility, effective beam collimation is extremely important to minimize radiation damage, prevent quenches of superconducting cavities, limit dose rates outside of the accelerator tunnel and prevent equipment damage. This paper describes the conceptual design of a collimation system, including detailed simulations to verify its effectiveness.

WEPFI066	The RF System for the MICE Experiment	2848
	K. Ronald, A.J. Dick, C.G. Whyte USTRAT/SUPA, Glasgow, United Kingdom P.A. Corlett STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom A.J. DeMello, D. Li, S.P. Virostek LBNL, Berkeley, California, USA A.F. Grant, A.J. Moss, C.J. White STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom P.M. Hanlet IIT, Chicago, Illinois, USA C. Hunt, K.R. Long, J. Pasternak Imperial College of Science and Technology, Department of Physics, London, United Kingdom T.H. Luo, D.J. Summers UMiss, University, Mississippi, USA A. Moretti, R.J. Pasquinelli, D.W. Peterson, R.P. Schultz, J.T. Volk Fermilab, Batavia, USA P.J. Smith Sheffield University, Sheffield, United Kingdom T. Stanley STFC/RAL, Chilton, Didcot, Oxon, United Kingdom Y. Torun Illinois Institute of Technology, Chicago, IL, USA
	The International Muon Ionisation Cooling Experiment (MICE) is designed to demonstrate the effectiveness of ionisation cooling to reduce the phase space footprint of a muon beam, principally to allow the subsequent acceleration of muons for next generation colliders and/or neutrino factories. The experiment (and indeed any subsequent accelerator cooling channel based on the same principles) poses certain unusual requirements on its RF system, whilst the precision measurement of the ionisation cooling process demands special diagnostics. This paper shall outline the key features of the RF system, including the LLRF control, the power amplifier chain, distribution network, cavities, tuners and couplers, all of which must operate in a high magnetic field environment. The RF diagnostics which, in conjunction with the other MICE diagnostics, shall allow detailed knowledge of the amplitude and phase of the acceleration field during the transit of each individual Muon shall also be outlined.

WEPFI072	Analysis of Breakdown Damage in an 805 MHz Pillbox Cavity for Muon Ionization Cooling R&D	2857
	D.L. Bowring, D. Li LBNL, Berkeley, California, USA A. Moretti, Y. Torun Fermilab, Batavia, USA
	When operating in multi-Tesla solenoidal magnetic fields, normal-conducting cavities exhibit RF breakdown at anomalously low gradients. This breakdown behavior may be due to field-emitted electrons, focused by the magnetic field into "beamlets" with relatively large current densities. These beamlets may then cause pulsed heating and cyclic fatigue damage on cavity interior surfaces. If this model is correct, materials with long radiation lengths (relative to copper) may alleviate the problem of RF breakdown in strong magnetic fields. To study this phenomenon, RF breakdown was induced on pairs of "buttons" in an 805 MHz pillbox cavity. The shape of the buttons creates a local enhancement of the surface electric field, such that breakdown occurs preferentially on the button surface. Beryllium and copper buttons were tested in order to evaluate the effect of radiation length on RF breakdown performance. This poster presents an analysis of the damage to these buttons and suggests a path forward for future materials R&D related to breakdown in strong magnetic fields.

WEPFI073	A Modular Cavity for Muon Ionization Cooling R&D	2860
	D.L. Bowring, A.J. DeMello, A.R. Lambert, D. Li, S.P. Virostek, M.S. Zisman LBNL, Berkeley, California, USA C. Adolphsen, L. Ge, A.A. Haase, K.H. Lee, Z. Li, D.W. Martin SLAC, Menlo Park, California, USA D.M. Kaplan Illinois Institute of Technology, Chicago, Illinois, USA T.H. Luo, D.J. Summers UMiss, University, Mississippi, USA A. Moretti, M.A. Palmer, R.J. Pasquinelli, Y. Torun Fermilab, Batavia, USA R.B. Palmer BNL, Upton, Long Island, New York, USA
	The Muon Accelerator Program (MAP) collaboration is developing an ionization cooling channel for muon beams. Ionization cooling channel designs call for the operation of high-gradient, normal-conducting RF cavities in multi-Tesla solenoidal magnetic fields. However, strong magnetic fields have been shown to limit the maximum achievable gradient in RF cavities. This gradient limit is characterized by RF breakdown and damage to the cavity surface. To study this issue, we have developed an experimental program based on a modular pillbox cavity operating at 805 MHz. The modular cavity design allows for the evaluation of different cavity materials - such as beryllium - which may ameliorate or circumvent RF breakdown triggers. Modular cavity components may furthermore be prepared with different surface treatments, such as high-temperature baking or chemical polishing. This poster presents the design and experimental status of the modular cavity, as well as future plans for the experimental program.

WEPFI091	Design of a Normal-conducting RF-dipole Deflecting Cavity	2911
	T.H. Luo, D.J. Summers UMiss, University, Mississippi, USA D. Li LBNL, Berkeley, California, USA
	In this paper we present a novel design of a CW normal conducting RF deflecting cavity. The cavity is designed into a dipole-like structure, resulting a high (R/Q)_transverse. The geometry at high H field is optimized to lower the surface peak power. We will show the design of a 325 MHz and 163 MHz cavity based on this structure and compare their performances with their superconducting counterparts.

WEPFI092	Multipacting Simulation of the MICE 201 MHz RF Cavity	2914
	T.H. Luo, D.J. Summers UMiss, University, Mississippi, USA D.L. Bowring, A.J. DeMello, D. Li, P. Pan, S.P. Virostek LBNL, Berkeley, California, USA L. Ge SLAC, Menlo Park, California, USA
	The international Muon Ionization Cooling Experiment (MICE) aims to demonstrate transverse cooling of muon beams by ionization. The MICE ionization cooling channel requires eight 201-MHz normal conducting RF cavities to compensate for the longitudinal beam energy loss in the cooling channel. Multipacting is a resonant electron discharge produced by the synchronization of emitted electrons with the RF fields, which can cause breakdown at high power RF operation. In this paper, we present the study of the multipacting effect in the MICE 201 MHz cavities with the SLAC ACE3P code. The simulation is carried out in the cavity body, the RF coupler region, and the coaxial waveguide, with the external magnetic field from the Coupling Coil. We will identify potential RF breakdowns due to multipacting and propose a solution to suppress them.

THPME047	Progress of the RFQ Accelerator for PXIE	3618
	D. Li, M.D. Hoff, A.R. Lambert, J.W. Staples, S.P. Virostek LBNL, Berkeley, California, USA T.H. Luo UMiss, University, Mississippi, USA S. Nagaitsev, G.V. Romanov, A.V. Shemyakin, R.P. Stanek, J. Steimel Fermilab, Batavia, USA
	Funding: This work is supported by the Office of Science, United States Department of Energy under DOE contract DE-AC02-05CH11231. The proposed Project X Injector Experiment (PXIE) is currently under development at Fermilab. PXIE is an R&D test accelerator that will replicate the front-end portion of Project X. The PXIE accelerator complex consists of a H⁻ ion source(s), low-energy beam transport (LEBT), 162.5 MHz normal conducting CW Radio-Frequency-Quadrupole (RFQ) accelerator, medium-energy beam transport (MEBT), broad-band beam chopper(s) and two superconducting cryomodules. In this paper, we will review and present recent progress of the PXIE RFQ, which will include an overview of the RFQ beam dynamics design, RF structure design, detailed thermal and mechanical analyses, fabrication test results and fabrication plan and schedule.

THPME048	Assembly and Test of a Modified Spectrometer Solenoid for MICE	3621
	S.P. Virostek, D. Li, P. Pan, S. Prestemon LBNL, Berkeley, California, USA R. Preece STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
	Funding: This work is supported by the Office of Science, US-DOE under DOE contract DE-AC02-05CH11231. The MICE superconducting spectrometer solenoids have been modified and rebuilt as a result of the testing done in 2008, 2009 and 2010. The number of two-stage cryocoolers was increased from three in 2009 to five in the modified magnet. The new shield for the spectrometer solenoid is fabricated primarily from 1100-O aluminum instead of 6061-T6 aluminum used in the former versions of the magnet. The thermal connection between the shield and the first-stage of the cold heads has been improved to reduce the temperature drop between the shield and the coolers. As a result of these changes, the first-stage temperatures for the coolers are below 45K, which resulted in an increase in the refrigeration generated by the cooler second stages. The quench protection system has been altered in order to provide additional protection to the magnet in the event of a lead failure between the magnet power supply and the magnet coils. The quality of the shield and cold mass MLI wrap has also been improved. Details of the modifications and test results demonstrating improved magnet performance are presented in this paper.