LINAC2016 - Table of Session: THOP (Oral Poster Session)

Paper	Title	Page
THOP01	Experimental Study of Nucleation for Nb3Sn Diffusion Coatings on Niobium SRF Cavities	740
SPWR042	use link to see paper's listing under its alternate paper code
THPRC002	use link to see paper's listing under its alternate paper code
	U. Pudasaini, M.J. Kelley The College of William and Mary, Williamsburg, Virginia, USA G.V. Eremeev, M.J. Kelley, C.E. Reece JLab, Newport News, Virginia, USA
	Funding: Partially authored by Jefferson Science Associates under Contract No. DE-AC05-06OR23177. Work at William & Mary supported by Office of High Energy Physics under grant SC0014475 Nb3Sn has the potential to achieve superior performance both in terms of operating temperature (4.2 K vs 2 K) and accelerating gradient resulting in significant reduction in both initial and operating costs of SRF linacs. Cavity interior surface coatings are obtained by two-step vapor diffusion: nucleation followed by deposition. To gain more understanding of nucleation and its effect on the subsequent coating, we investigated the effect of varying parameters in a typical tin/tin chloride process. We report findings obtained by SEM/EDS, AFM, SAM and other materials characterization approaches.
	Slides THOP01 [2.784 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP01
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THOP02	Investigation of Nitrogen Absorption Rate and Nitride Growth on SRF Cavity Grade RRR Niobium as a Function of Furnace Temperature	744
THPRC003	use link to see paper's listing under its alternate paper code
	A.D. Palczewski, C.E. Reece JLab, Newport News, Virginia, USA M.J. Kelley The College of William and Mary, Williamsburg, Virginia, USA J. Tuggle Virginia Polytechnic Institute and State University, Blacksburg, USA
	Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The current state of the art processing of niobium superconducting radio frequency cavities with nitrogen diffusion is performed at 800C in a furnace with a partial pressure of approximately ~20 mtorr of nitrogen. Multiple studies have shown the bulk of the nitrogen absorbed by the niobium forms a thick (1-3 microns) non-superconducting nitride layer which must be removed to produce optimal RF results. The depth profiling of interstitial nitrogen and surface nitrides has already been probed using SIMS measurements. These measurements have also been modeled by extrapolating data from nitride growth studies performed at atmospheric pressure and temperatures above 1000 C (). One open question is whether there is a diffusion zone at lower temperature in which the niobium will absorb nitrogen but not create a non-superconducting nitride layer; or is the absorption of nitrogen only possible by first forming a nitride buffer layer which then frees up nitrogen for absorption. A systematic study of absorption rate vs. temperature and correlated SIMS measurements needs to be performed to answer this question. We report on the absorption rate vs. temperature from 400 C to 900 C of cavity grade niobium with metallurgically flat witness samples. The witness samples surface depth profile of NbN via SIMS's will be presented and correlated to the absorption. * Gonnella et al., Proceedings of SRF2015 Pre-release MOPB042 (2015) ** Tuggle et al., Investigation of Low-Level Nitrogen in Niobium by Secondary Ion Mass Spectrometry, these proceedings (2016)
	Poster THOP02 [2.235 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP02
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THOP03	Cold Bead-Pull Test Stand for SRF Cavities	748
THPRC004	use link to see paper's listing under its alternate paper code
	A.V. Vélez, A. Frahm, J. Knobloch, A. Neumann HZB, Berlin, Germany
	Bead-pull measurements represent a final step in the fabrication process of an SRF cavity. These tests allow to characterize the flatness of the field profile in order to perform mechanical tuning if needed. These test has been always performed at room temperature, where material properties differ from the superconducting state properties. Still questions like mechanical deformation due to assymetrical thermal shrincage have not yet been answered experimentaly. In this paper, an upgrade of the former Cold-Bead pull system developed by HZB [1] is presented. This test stand is capable of holding a 9-cell Tesla cavity at LHe temperature providing a realistic insight to cavity parameters under realistic conditions. A copper test pill-box is placed in series with the multi-cell cavity in order to perform 1.8K calibration of the bead. Results will be presented on this paper and compared to electromagnetic simulations.
	Slides THOP03 [2.731 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP03
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THOP04	Measurements of the Beam Break-Up Threshold Current at the Recirculating Electron Accelerator S-DALINAC	751
THPLR001	use link to see paper's listing under its alternate paper code
	T. Kürzeder, M. Arnold, L.E. Jürgensen, J. Pforr, N. Pietralla TU Darmstadt, Darmstadt, Germany F. Hugpresenter IKP, Mainz, Germany
	Funding: *Supported by the German Federal Ministry for Education and Research (BMBF) under Grant No. 05K13RDA. Linear accelerators, in particular those with a recirculating design and superconducting cavities, have to deal with the problem of Beam Break-Up (BBU). This instability can limit the maximum beam current in such accelerators. Knowing the effectiveness of prevention strategies is of great interest especially for future accelerators like energy recovery linacs (ERL) which aim for high beam currents. One option is to optimize the cavities and higher order mode couplers of those machines. In addition one may adapt the beam line lattice for further suppressing BBU. The superconducting recirculating accelerator S-DALINAC at the Technische Universität Darmstadt provides electron beams in c.w. for nuclear physics experiments since 1991. As the SRF components were never optimized for higher order mode suppression the S-DALINAC suffers from BBU at relatively low beam currents of a few μA. While those currents are sufficient for most nuclear physics experiments we can investigate BBU with respect to the beam optics. We will report on first measurements of threshold currents at different beam energies of the S-DALINAC. The results of a first test to increase the BBU limit by using skew quadrupoles will be presented.
	Slides THOP04 [1.473 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP04
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THOP05	Status and Operation of the ALBA Linac	754
THPLR002	use link to see paper's listing under its alternate paper code
	R. Muñoz Horta, D. Lanaia, F. Pérez ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
	The pre-injector of the ALBA Light Source is a Linac that delivers electrons up to a maximum energy of 125 MeV. It consist in a pre-bunching, a bunching and two accelerating sections feed by two 35 MW klystrons. Since July 2014, ALBA is operating in top-up mode, and the Linac is delivering 110 MeV electrons in multibunch mode every 20 minutes. Recently, new injection modes have been implemented and successfully tested. For one side, injection to the ALBA Booster is now also available with only one of the two klystrons in operation, and the Linac delivering a 67 MeV beam. On the other hand, the Linac single bunch mode has been integrated to the top-up operation application. By means of an algorithm, single bunch mode operation provides any kind of filling pattern in the ALBA storage ring, with single bunch shots injected to those buckets with lowest current. The performance of the Linac beam operated in these different modes is reported.
	Slides THOP05 [0.604 MB]
	Poster THOP05 [4.967 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP05
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THOP06	Novel Scheme to Tune RF Cavities Using Reflected Power	757
SPWR034	use link to see paper's listing under its alternate paper code
THPLR058	use link to see paper's listing under its alternate paper code
	R. Leewe, K. Fong, Z. Shahriari TRIUMF, Vancouver, Canada M. Moallem SFU, Surrey, Canada
	Tuning of the natural resonance frequency of an RF cavity is essential for accelerator structures to achieve efficient beam acceleration and to reduce power requirements. Typically operational cavities are tuned using phase comparison techniques. The phase measurement is subject to temperature drifts and renders this technique labor and time intensive. To eliminate the phase measurement, reduce human oversight and speed up the start-up time for each cavity, this paper presents a control scheme that relies solely on the reflected power measurements. A sliding mode extremum seeking algorithm is used to minimize the reflected power. To avoid tuning motor abrasion, a variable gain minimizes motor movement around the optimum operating point. The system has been tested and is fully commissioned on two drift tube linear accelerator tanks in TRIUMF's ISAC I linear accelerator. Experimental results show that the resonance frequency can be tuned to its optimum operating point while the start-up time of a single cavity and the accompanied human oversight are significantly decreased.
	Poster THOP06 [0.244 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP06
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THOP08	Beam Commissioning of the i-BNCT Linac	760
THPLR056	use link to see paper's listing under its alternate paper code
	F. Naito, S. Anami, Z. Fang, K. Futatsukawa, Y. Honda, Y. Hori, M. Kawamura, H. Kobayashi, T. Kurihara, T. Miura, T. Miura, T. Miyajima, T. Obina, F. Qiu, Y. Sato, T. Shibata, M. Shimamoto, A. Takagi, E. Takasaki, M. Uota KEK, Ibaraki, Japan S. Fujikura ICEPP, Tokyo, Japan K. Ikegami J-PARC, KEK & JAEA, Ibaraki-ken, Japan H. Kumada, Su. Tanaka Tsukuba University, Graduate School of Comprehensive Human Sciences, Ibaraki, Japan Y. Liu, T. Maruta KEK/JAEA, Ibaraki-Ken, Japan A. Miura JAEA/J-PARC, Tokai-mura, Japan N. Nagura, T. Ohba Nippon Advanced Technology Co., Ltd., Tokai, Japan T. Onishi Tsukuba University, Ibaraki, Japan T. Ouchi ATOX, Ibaraki, Japan
	The beam commissioning of the linac for the boron neutron capture therapy of Ibaraki prefecture (i-BNCT) has been started. The accelerator of i-BNCT consists of the 3-MeV RFQ and 8-MeV DTL. The design of RF structure of them is based on the J-PARC linac. After the first demonstration of neutron production on December 2015, significant modifications to the linac were given in order to increase the operation stability and the beam power. The progress of the beam commissioning of the i-BNCT will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP08
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THOP09	Tuning of the CERN 750 MHz RFQ for Medical Applications	763
THPLR055	use link to see paper's listing under its alternate paper code
	B. Koubek, Y. Cuvet, A. Grudiev, C. Rossi, M.A. Timmins CERN, Geneva, Switzerland
	CERN has built a compact 750 MHz RFQ as an injector for a hadron therapy linac. This RFQ was designed to accelerate protons to an energy of 5 MeV within only 2 m length. It is divided into four segments and equipped with 32 tuners in total. The RFQ length corresponds to 5λ which is considered to be close to the limit for simple field adjustment using tuners. Nevertheless the high frequency results in a sensitive structure and requires careful tuning by means of the alignment of the pumping ports and fixed tuners. This paper gives an overview of the tuning procedure and bead pull measurements of the RFQ.
	Slides THOP09 [16.367 MB]
	Poster THOP09 [23.832 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP09
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THOP10	Design and Commissioning of FRIB Multipacting-Free Fundamental Power Coupler	767
THPLR010	use link to see paper's listing under its alternate paper code
	Z. Zheng, J.T. Popielarski, K. Saito, S. Stark, T. Xu, Y. Yamazaki FRIB, East Lansing, USA
	Funding: *Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 The original Fundamental Power Coupler (FPC) of Half-Wave Resonator (HWR) for the Facility of Rare Isotope Beams (FRIB) requires multipacting conditioning at operating RF power which is up to 5 kW Continue Wave (CW). Conditioning takes a lot of time and RF power, and its elimination is highly desirable. To significantly shorten the RF conditioning, we developed a multipacting-free coupler design. This paper reports the latest progress in the optimization and prototype tests of multipacting-free coupler. The choke structure is removed and coupler geometry is further modified to protect the coupler RF window from the electron bombardment. The comparison result of multipacting-free coupler with original coupler was performed on automatic conditioning system, which showed significantly time reducing for RF conditioning.
	Slides THOP10 [2.442 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP10
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THOP11	Ultra-Short Bunch Electron Injector for Awake	770
THPLR071	use link to see paper's listing under its alternate paper code
	S. Döbert CERN, Geneva, Switzerland
	The proton driven plasma wake field acceleration experiment AWAKE at CERN will start at the end of this year. In 2017 an S-band electron injector producing bunches of a few ps length will be added to probe the wake fields stimulated by a driving proton beam. In the future this electron injector will have to be upgraded to obtain electron bunches with a length of 100 - 200 fs in order to demonstrate injection into a single bucket of the plasma wave and therefore sustainable acceleration with low energy spread. Target bunch parameters for the study are a bunch charge of 100 pC, 100 fs bunch length, an emittance smaller than 2 mm mrad and a beam energy of 100 MeV. The status of a study to achieve these parameters using X-band accelerator hardware and velocity bunching will be presented.
	Slides THOP11 [2.733 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP11
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THOP12	Electron Linac Upgrade for Thomx Project	773
SPWR001	use link to see paper's listing under its alternate paper code
THPLR072	use link to see paper's listing under its alternate paper code
	L. Garolfi, C. Bruni, M. El Khaldi LAL, Orsay, France N. Faure, A. Perez Delaume PMB-ALCEN, PEYNIER, France
	The injector Linac for Thomx * consists of an electron gun and S-band accelerating section. The RF gun is a 2.5 cells photo-injector able to provide electron bunches with 5 MeV energy. During the commissioning phase, a standard S-band accelerating section is able to achieve around 50 MeV corresponding to around 45 keV X-rays energy. Since the maximum targeted X-ray energy is 90 keV, the Linac design will provide a beam energy of 70 MeV. The Linac upgrade of the machine covers many different aspects. The purpose is to increase the compactness of the accelerator complex whereas the beam properties for ring injection are kept. A LAL Orsay-PMB ALCEN collaboration has been established. The program foresees the RF design, prototyping and power tests of a high-gradient compact S-band accelerating structure. To fulfill the technical specifications at the interaction point, the Linac must be carefully designed. Beam dynamics simulations have been performed for optimizing the emittance and the energy spread for the ring entrance. The best set of parameters together with the effect of the accelerating section to the beam dynamics at the end of the LINAC will be presented. * A. Variola, et al, "The Thomx Project Status", Proceedings of IPAC2014, Dresden, Germany.
	Slides THOP12 [1.726 MB]
	Poster THOP12 [0.823 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP12
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Paper

Title

Page

THOP01

Experimental Study of Nucleation for Nb3Sn Diffusion Coatings on Niobium SRF Cavities

740

SPWR042

use link to see paper's listing under its alternate paper code

THPRC002

use link to see paper's listing under its alternate paper code

U. Pudasaini, M.J. Kelley
The College of William and Mary, Williamsburg, Virginia, USA
G.V. Eremeev, M.J. Kelley, C.E. Reece
JLab, Newport News, Virginia, USA

Funding: Partially authored by Jefferson Science Associates under Contract No. DE-AC05-06OR23177. Work at William & Mary supported by Office of High Energy Physics under grant SC0014475
Nb3Sn has the potential to achieve superior performance both in terms of operating temperature (4.2 K vs 2 K) and accelerating gradient resulting in significant reduction in both initial and operating costs of SRF linacs. Cavity interior surface coatings are obtained by two-step vapor diffusion: nucleation followed by deposition. To gain more understanding of nucleation and its effect on the subsequent coating, we investigated the effect of varying parameters in a typical tin/tin chloride process. We report findings obtained by SEM/EDS, AFM, SAM and other materials characterization approaches.

Slides THOP01 [2.784 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP01

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THOP02

Investigation of Nitrogen Absorption Rate and Nitride Growth on SRF Cavity Grade RRR Niobium as a Function of Furnace Temperature

744

THPRC003

use link to see paper's listing under its alternate paper code

A.D. Palczewski, C.E. Reece
JLab, Newport News, Virginia, USA
M.J. Kelley
The College of William and Mary, Williamsburg, Virginia, USA
J. Tuggle
Virginia Polytechnic Institute and State University, Blacksburg, USA

Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The current state of the art processing of niobium superconducting radio frequency cavities with nitrogen diffusion is performed at 800C in a furnace with a partial pressure of approximately ~20 mtorr of nitrogen. Multiple studies have shown the bulk of the nitrogen absorbed by the niobium forms a thick (1-3 microns) non-superconducting nitride layer which must be removed to produce optimal RF results. The depth profiling of interstitial nitrogen and surface nitrides has already been probed using SIMS measurements. These measurements have also been modeled by extrapolating data from nitride growth studies performed at atmospheric pressure and temperatures above 1000 C (**). One open question is whether there is a diffusion zone at lower temperature in which the niobium will absorb nitrogen but not create a non-superconducting nitride layer; or is the absorption of nitrogen only possible by first forming a nitride buffer layer which then frees up nitrogen for absorption. A systematic study of absorption rate vs. temperature and correlated SIMS measurements needs to be performed to answer this question. We report on the absorption rate vs. temperature from 400 C to 900 C of cavity grade niobium with metallurgically flat witness samples. The witness samples surface depth profile of NbN via SIMS's will be presented and correlated to the absorption.**
* Gonnella et al., Proceedings of SRF2015 Pre-release MOPB042 (2015)
** Tuggle et al., Investigation of Low-Level Nitrogen in Niobium by Secondary Ion Mass Spectrometry, these proceedings (2016)

Poster THOP02 [2.235 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP02

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THOP03

Cold Bead-Pull Test Stand for SRF Cavities

748

THPRC004

use link to see paper's listing under its alternate paper code

A.V. Vélez, A. Frahm, J. Knobloch, A. Neumann
HZB, Berlin, Germany

Bead-pull measurements represent a final step in the fabrication process of an SRF cavity. These tests allow to characterize the flatness of the field profile in order to perform mechanical tuning if needed. These test has been always performed at room temperature, where material properties differ from the superconducting state properties. Still questions like mechanical deformation due to assymetrical thermal shrincage have not yet been answered experimentaly. In this paper, an upgrade of the former Cold-Bead pull system developed by HZB [1] is presented. This test stand is capable of holding a 9-cell Tesla cavity at LHe temperature providing a realistic insight to cavity parameters under realistic conditions. A copper test pill-box is placed in series with the multi-cell cavity in order to perform 1.8K calibration of the bead. Results will be presented on this paper and compared to electromagnetic simulations.

Slides THOP03 [2.731 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP03

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THOP04

Measurements of the Beam Break-Up Threshold Current at the Recirculating Electron Accelerator S-DALINAC

751

THPLR001

use link to see paper's listing under its alternate paper code

T. Kürzeder, M. Arnold, L.E. Jürgensen, J. Pforr, N. Pietralla
TU Darmstadt, Darmstadt, Germany
F. Hugpresenter
IKP, Mainz, Germany

Funding: *Supported by the German Federal Ministry for Education and Research (BMBF) under Grant No. 05K13RDA.
Linear accelerators, in particular those with a recirculating design and superconducting cavities, have to deal with the problem of Beam Break-Up (BBU). This instability can limit the maximum beam current in such accelerators. Knowing the effectiveness of prevention strategies is of great interest especially for future accelerators like energy recovery linacs (ERL) which aim for high beam currents. One option is to optimize the cavities and higher order mode couplers of those machines. In addition one may adapt the beam line lattice for further suppressing BBU. The superconducting recirculating accelerator S-DALINAC at the Technische Universität Darmstadt provides electron beams in c.w. for nuclear physics experiments since 1991. As the SRF components were never optimized for higher order mode suppression the S-DALINAC suffers from BBU at relatively low beam currents of a few μA. While those currents are sufficient for most nuclear physics experiments we can investigate BBU with respect to the beam optics. We will report on first measurements of threshold currents at different beam energies of the S-DALINAC. The results of a first test to increase the BBU limit by using skew quadrupoles will be presented.

Slides THOP04 [1.473 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP04

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THOP05

Status and Operation of the ALBA Linac

754

THPLR002

use link to see paper's listing under its alternate paper code

R. Muñoz Horta, D. Lanaia, F. Pérez
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

The pre-injector of the ALBA Light Source is a Linac that delivers electrons up to a maximum energy of 125 MeV. It consist in a pre-bunching, a bunching and two accelerating sections feed by two 35 MW klystrons. Since July 2014, ALBA is operating in top-up mode, and the Linac is delivering 110 MeV electrons in multibunch mode every 20 minutes. Recently, new injection modes have been implemented and successfully tested. For one side, injection to the ALBA Booster is now also available with only one of the two klystrons in operation, and the Linac delivering a 67 MeV beam. On the other hand, the Linac single bunch mode has been integrated to the top-up operation application. By means of an algorithm, single bunch mode operation provides any kind of filling pattern in the ALBA storage ring, with single bunch shots injected to those buckets with lowest current. The performance of the Linac beam operated in these different modes is reported.

Slides THOP05 [0.604 MB]

Poster THOP05 [4.967 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP05

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THOP06

Novel Scheme to Tune RF Cavities Using Reflected Power

757

SPWR034

use link to see paper's listing under its alternate paper code

THPLR058

use link to see paper's listing under its alternate paper code

R. Leewe, K. Fong, Z. Shahriari
TRIUMF, Vancouver, Canada
M. Moallem
SFU, Surrey, Canada

Tuning of the natural resonance frequency of an RF cavity is essential for accelerator structures to achieve efficient beam acceleration and to reduce power requirements. Typically operational cavities are tuned using phase comparison techniques. The phase measurement is subject to temperature drifts and renders this technique labor and time intensive. To eliminate the phase measurement, reduce human oversight and speed up the start-up time for each cavity, this paper presents a control scheme that relies solely on the reflected power measurements. A sliding mode extremum seeking algorithm is used to minimize the reflected power. To avoid tuning motor abrasion, a variable gain minimizes motor movement around the optimum operating point. The system has been tested and is fully commissioned on two drift tube linear accelerator tanks in TRIUMF's ISAC I linear accelerator. Experimental results show that the resonance frequency can be tuned to its optimum operating point while the start-up time of a single cavity and the accompanied human oversight are significantly decreased.

Poster THOP06 [0.244 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP06

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THOP08

Beam Commissioning of the i-BNCT Linac

760

THPLR056

use link to see paper's listing under its alternate paper code

F. Naito, S. Anami, Z. Fang, K. Futatsukawa, Y. Honda, Y. Hori, M. Kawamura, H. Kobayashi, T. Kurihara, T. Miura, T. Miura, T. Miyajima, T. Obina, F. Qiu, Y. Sato, T. Shibata, M. Shimamoto, A. Takagi, E. Takasaki, M. Uota
KEK, Ibaraki, Japan
S. Fujikura
ICEPP, Tokyo, Japan
K. Ikegami
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
H. Kumada, Su. Tanaka
Tsukuba University, Graduate School of Comprehensive Human Sciences, Ibaraki, Japan
Y. Liu, T. Maruta
KEK/JAEA, Ibaraki-Ken, Japan
A. Miura
JAEA/J-PARC, Tokai-mura, Japan
N. Nagura, T. Ohba
Nippon Advanced Technology Co., Ltd., Tokai, Japan
T. Onishi
Tsukuba University, Ibaraki, Japan
T. Ouchi
ATOX, Ibaraki, Japan

The beam commissioning of the linac for the boron neutron capture therapy of Ibaraki prefecture (i-BNCT) has been started. The accelerator of i-BNCT consists of the 3-MeV RFQ and 8-MeV DTL. The design of RF structure of them is based on the J-PARC linac. After the first demonstration of neutron production on December 2015, significant modifications to the linac were given in order to increase the operation stability and the beam power. The progress of the beam commissioning of the i-BNCT will be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP08

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THOP09

Tuning of the CERN 750 MHz RFQ for Medical Applications

763

THPLR055

use link to see paper's listing under its alternate paper code

B. Koubek, Y. Cuvet, A. Grudiev, C. Rossi, M.A. Timmins
CERN, Geneva, Switzerland

CERN has built a compact 750 MHz RFQ as an injector for a hadron therapy linac. This RFQ was designed to accelerate protons to an energy of 5 MeV within only 2 m length. It is divided into four segments and equipped with 32 tuners in total. The RFQ length corresponds to 5λ which is considered to be close to the limit for simple field adjustment using tuners. Nevertheless the high frequency results in a sensitive structure and requires careful tuning by means of the alignment of the pumping ports and fixed tuners. This paper gives an overview of the tuning procedure and bead pull measurements of the RFQ.

Slides THOP09 [16.367 MB]

Poster THOP09 [23.832 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP09

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THOP10

Design and Commissioning of FRIB Multipacting-Free Fundamental Power Coupler

767

THPLR010

use link to see paper's listing under its alternate paper code

Z. Zheng, J.T. Popielarski, K. Saito, S. Stark, T. Xu, Y. Yamazaki
FRIB, East Lansing, USA

Funding: *Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The original Fundamental Power Coupler (FPC) of Half-Wave Resonator (HWR) for the Facility of Rare Isotope Beams (FRIB) requires multipacting conditioning at operating RF power which is up to 5 kW Continue Wave (CW). Conditioning takes a lot of time and RF power, and its elimination is highly desirable. To significantly shorten the RF conditioning, we developed a multipacting-free coupler design. This paper reports the latest progress in the optimization and prototype tests of multipacting-free coupler. The choke structure is removed and coupler geometry is further modified to protect the coupler RF window from the electron bombardment. The comparison result of multipacting-free coupler with original coupler was performed on automatic conditioning system, which showed significantly time reducing for RF conditioning.

Slides THOP10 [2.442 MB]

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THOP11

Ultra-Short Bunch Electron Injector for Awake

770

THPLR071

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S. Döbert
CERN, Geneva, Switzerland

The proton driven plasma wake field acceleration experiment AWAKE at CERN will start at the end of this year. In 2017 an S-band electron injector producing bunches of a few ps length will be added to probe the wake fields stimulated by a driving proton beam. In the future this electron injector will have to be upgraded to obtain electron bunches with a length of 100 - 200 fs in order to demonstrate injection into a single bucket of the plasma wave and therefore sustainable acceleration with low energy spread. Target bunch parameters for the study are a bunch charge of 100 pC, 100 fs bunch length, an emittance smaller than 2 mm mrad and a beam energy of 100 MeV. The status of a study to achieve these parameters using X-band accelerator hardware and velocity bunching will be presented.

Slides THOP11 [2.733 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP11

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THOP12

Electron Linac Upgrade for Thomx Project

773

SPWR001

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THPLR072

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L. Garolfi, C. Bruni, M. El Khaldi
LAL, Orsay, France
N. Faure, A. Perez Delaume
PMB-ALCEN, PEYNIER, France

The injector Linac for Thomx * consists of an electron gun and S-band accelerating section. The RF gun is a 2.5 cells photo-injector able to provide electron bunches with 5 MeV energy. During the commissioning phase, a standard S-band accelerating section is able to achieve around 50 MeV corresponding to around 45 keV X-rays energy. Since the maximum targeted X-ray energy is 90 keV, the Linac design will provide a beam energy of 70 MeV. The Linac upgrade of the machine covers many different aspects. The purpose is to increase the compactness of the accelerator complex whereas the beam properties for ring injection are kept. A LAL Orsay-PMB ALCEN collaboration has been established. The program foresees the RF design, prototyping and power tests of a high-gradient compact S-band accelerating structure. To fulfill the technical specifications at the interaction point, the Linac must be carefully designed. Beam dynamics simulations have been performed for optimizing the emittance and the energy spread for the ring entrance. The best set of parameters together with the effect of the accelerating section to the beam dynamics at the end of the LINAC will be presented.
* A. Variola, et al, "The Thomx Project Status", Proceedings of IPAC2014, Dresden, Germany.

Slides THOP12 [1.726 MB]

Poster THOP12 [0.823 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP12

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