LINAC2014 - List of Authors (Doebert, S.)

Paper	Title	Page
MOPP034	Beam Dynamics Studies of the CLIC Drive Beam Injector	131
SUPG027	use link to see paper's listing under its alternate paper code
	S. Sanaye Hajari, S. Döbert, H. Shaker CERN, Geneva, Switzerland S. Sanaye Hajari, H. Shaker IPM, Tehran, Iran
	In the Compact Linear Collider (CLIC) the RF power for the acceleration of the Main Beam is extracted from a high-current Drive Beam that runs parallel with the main linac. The beam in the Drive Beam Accelerator is phase coded. This means only every second accelerator bucket is occupied. However, a few percent of particles are captured in wrong buckets, called satellite bunches. The phase coding is done via a sub-harmonic bunching system operating at a half the acceleration frequency. The beam dynamics of the Drive Beam injector complex has been studied in detail and optimised. The model consists of a thermionic gun, the bunching system followed by some accelerating structures and a magnetic chicane. The bunching system contains three sub-harmonic bunchers, a prebuncher and a tapered travelling wave buncher all embedded in a solenoidal magnetic field. The simulation of the beam dynamics has been carried out with PARMELA with the goal of optimising the overall bunching process and in particular decreasing the satellite population and the beam loss in magnetic chicane and in transverse plane limiting the beam emittance growth.

TUPP028	Beam Tests at the CLIC Test Facility, CTF3	487
	R. Corsini, S. Döbert, W. Farabolini, D. Gamba, J.L. Navarro Quirante, T. Persson, P.K. Skowronski, F. Tecker CERN, Geneva, Switzerland W. Farabolini CEA/DSM/IRFU, France D. Gamba JAI, Oxford, United Kingdom
	The CLIC Test Facility CTF3 has been built at CERN by the Compact Linear Collider (CLIC) International Collaboration, in order to prove the main feasibility issues of the two-beam acceleration technology on which the collider is based. After the successful completion of its initial task, CTF3 is continuing its experimental program in order to give further indications on cost and performance issues, to act as a test bed for the CLIC technology, and to conduct beam experiments aimed at mitigating technological risks. In this paper we discuss the status of the ongoing experiments and present the more recent results, including improvements in beam quality and stability.

TUPP029	Diagnostics and Analysis Techniques for High Power X-Band Accelerating Structures	490
SUPG002	use link to see paper's listing under its alternate paper code
	A. Degiovanni, S. Döbert, W. Farabolini, I. Syratchev, W. Wuensch CERN, Geneva, Switzerland J. Giner Navarro IFIC, Valencia, Spain J. Tagg National Instruments Switzerland, Ennetbaden, Switzerland B.J. Woolley Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
	The study of high gradient limitations due to RF breakdowns is extremely important for the CLIC project. A series of diagnostic tools and analysis techniques have been developed in order to monitor and characterize the behaviour of CLIC accelerating structures under high power operation in the first CERN X-band klystron-based test stand (Xbox1). The data collected during the last run on a TD26r05 structure are presented in this paper. From the analysis of the RF power and phases, the location of the breakdowns inside the structure could be determined. Other techniques based on the field emitted dark current signals collected by Faraday cups placed at the two extremities of the structure have also been investigated. The results of these analyses are reported and discussed.

TUPP030	Design of a High Average Current Electron Source for the CLIC Drive Beam Injector	493
	S. Döbert, N. Chritin CERN, Geneva, Switzerland B. Cadilhon, B. Cassany, J. Gardelle, K. Pepitone CEA, LE BARP cedex, France
	The drive beam injector for CLIC needs to deliver a 4.2 A electron beam for a duration of 140 μs with a repetition rate of 50 Hz. The shot to shot and flat top current stability has to be better than 0.1% to guarantee the beam stability required for CLIC. Based on the experience with the CTF3 injector a thermionic high voltage gun with a gridded cathode has been designed together with a sub-harmonic bunching system to achieve these requirements. The grid will allow controlling the current and eventually feedback on the flattop shape. The gun will operate at 140 kV and an emittance of 14 mm mrad can be obtained. The paper describes the design approach and the results of the systematic electromagnetic simulations to optimize the gun. Care was taken during the mechanical design of the gun to obtain a modular design allowing adjusting for different beam currents and cathode sizes.

TUPP033	Effect of Beam-Loading on the Breakdown Rate of High Gradient Accelerating Structures	499
TUPOL08	use link to see paper's listing under its alternate paper code
	J.L. Navarro Quirante, R. Corsini, A. Degiovanni, S. Döbert, A. Grudiev, O. Kononenko, G. McMonagle, S.F. Rey, A. Solodko, I. Syratchev, F. Tecker, L. Timeo, B.J. Woolley, X.W. Wu, W. Wuensch CERN, Geneva, Switzerland O. Kononenko SLAC, Menlo Park, California, USA A. Solodko JINR, Dubna, Moscow Region, Russia J. Tagg National Instruments Switzerland, Ennetbaden, Switzerland B.J. Woolley Cockcroft Institute, Lancaster University, Lancaster, United Kingdom X.W. Wu TUB, Beijing, People's Republic of China
	The Compact Linear Collider (CLIC) is a study for a future room temperature electron-positron collider with a maximum center-of-mass energy of 3 TeV. To efficiently achieve such high energy, the project relies on a novel two beam acceleration concept and on high-gradient accelerating structures working at 100 MV/m. In order to meet the luminosity requirements, the break-down rate in these high-field structures has to be kept below 10 per billion. Such gradients and breakdown rates have been demonstrated by high-power RF testing several 12 GHz structures. However, the presence of beam-loading modifies the field distribution for the structure, such that a higher input power is needed in order to achieve the same accelerating gradient as the unloaded case. The potential impact on the break-down rate was never measured before. In this paper we present an experiment located at the CLIC Test Facility CTF3 recently proposed in order to quantify this effect, layout and hardware status, and discuss its first results.
	Slides TUPP033 [1.970 MB]
	Poster TUPP033 [2.355 MB]

THPP028	Design and Beamloading-Simulations of a Pre-Bunching Cavity for the CLIC Drive Beam Injector	895
SUPG001	use link to see paper's listing under its alternate paper code
	M. Dayyani Kelisani, S. Döbert, H. Shaker CERN, Geneva, Switzerland H. Shaker IPM, Tehran, Iran
	The CLIC project is developing a multi-TeV center-of-mass electron-positron collider based on high-gradient, room-temperature accelerating structures and a novel two-beam RF power generation scheme. The RF power for the CLIC accelerating structures is provided by the so-called drive beam which is a low energy, high current electron beam. The drive beam will be generated from a high current (up to 5 A) pulsed (142μs) thermionic electron gun and then followed by a bunching system. The bunching system is composed of three sub-harmonic bunchers operating at a frequency of 499.75 MHz, a pre-buncher and a traveling wave buncher both operating at 999.5MHz. The pre-buncher cavity, which has a great importance on minimization the satellite population, should be designed with special consideration of the high beam loading effect due to the high current beam crossing the cavity. In this work we report on RF design, analytical beam loading calculations and simulations for the CLIC drive beam injector pre-buncher cavity.

THPP035	Deceleration Measurements of an Electron Beam in the CLIC Test Facility 3	920
SUPG003	use link to see paper's listing under its alternate paper code
	R.L. Lillestøl, S. Döbert CERN, Geneva, Switzerland E. Adli University of Oslo, Oslo, Norway
	The Test Beam Line at the CLIC Test Facility 3 at CERN is a proof-of-principle of the future CLIC decelerators, which will extract a large amount of beam energy for acceleration of the main CLIC beams. The current beamline consists of a FODO lattice with 13 Power Extraction and Transfer Structures (PETS). We discuss beam deceleration measurements of up to 37 %, taking into account effects from the bunch length and the bunch phase. The 12 GHz phase is reproduced based on measurements in a PETS with an uncombined beam. The spectrometer measurements are also compared to predictions based on the beam current and on the produced rf power in the PETS, as well as particle tracking simulations with the Placet code.

Paper

Title

Page

MOPP034

Beam Dynamics Studies of the CLIC Drive Beam Injector

131

SUPG027

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

S. Sanaye Hajari, S. Döbert, H. Shaker
CERN, Geneva, Switzerland
S. Sanaye Hajari, H. Shaker
IPM, Tehran, Iran

In the Compact Linear Collider (CLIC) the RF power for the acceleration of the Main Beam is extracted from a high-current Drive Beam that runs parallel with the main linac. The beam in the Drive Beam Accelerator is phase coded. This means only every second accelerator bucket is occupied. However, a few percent of particles are captured in wrong buckets, called satellite bunches. The phase coding is done via a sub-harmonic bunching system operating at a half the acceleration frequency. The beam dynamics of the Drive Beam injector complex has been studied in detail and optimised. The model consists of a thermionic gun, the bunching system followed by some accelerating structures and a magnetic chicane. The bunching system contains three sub-harmonic bunchers, a prebuncher and a tapered travelling wave buncher all embedded in a solenoidal magnetic field. The simulation of the beam dynamics has been carried out with PARMELA with the goal of optimising the overall bunching process and in particular decreasing the satellite population and the beam loss in magnetic chicane and in transverse plane limiting the beam emittance growth.

TUPP028

Beam Tests at the CLIC Test Facility, CTF3

487

R. Corsini, S. Döbert, W. Farabolini, D. Gamba, J.L. Navarro Quirante, T. Persson, P.K. Skowronski, F. Tecker
CERN, Geneva, Switzerland
W. Farabolini
CEA/DSM/IRFU, France
D. Gamba
JAI, Oxford, United Kingdom

The CLIC Test Facility CTF3 has been built at CERN by the Compact Linear Collider (CLIC) International Collaboration, in order to prove the main feasibility issues of the two-beam acceleration technology on which the collider is based. After the successful completion of its initial task, CTF3 is continuing its experimental program in order to give further indications on cost and performance issues, to act as a test bed for the CLIC technology, and to conduct beam experiments aimed at mitigating technological risks. In this paper we discuss the status of the ongoing experiments and present the more recent results, including improvements in beam quality and stability.

TUPP029

Diagnostics and Analysis Techniques for High Power X-Band Accelerating Structures

490

SUPG002

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

A. Degiovanni, S. Döbert, W. Farabolini, I. Syratchev, W. Wuensch
CERN, Geneva, Switzerland
J. Giner Navarro
IFIC, Valencia, Spain
J. Tagg
National Instruments Switzerland, Ennetbaden, Switzerland
B.J. Woolley
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom

The study of high gradient limitations due to RF breakdowns is extremely important for the CLIC project. A series of diagnostic tools and analysis techniques have been developed in order to monitor and characterize the behaviour of CLIC accelerating structures under high power operation in the first CERN X-band klystron-based test stand (Xbox1). The data collected during the last run on a TD26r05 structure are presented in this paper. From the analysis of the RF power and phases, the location of the breakdowns inside the structure could be determined. Other techniques based on the field emitted dark current signals collected by Faraday cups placed at the two extremities of the structure have also been investigated. The results of these analyses are reported and discussed.

TUPP030

Design of a High Average Current Electron Source for the CLIC Drive Beam Injector

493

S. Döbert, N. Chritin
CERN, Geneva, Switzerland
B. Cadilhon, B. Cassany, J. Gardelle, K. Pepitone
CEA, LE BARP cedex, France

The drive beam injector for CLIC needs to deliver a 4.2 A electron beam for a duration of 140 μs with a repetition rate of 50 Hz. The shot to shot and flat top current stability has to be better than 0.1% to guarantee the beam stability required for CLIC. Based on the experience with the CTF3 injector a thermionic high voltage gun with a gridded cathode has been designed together with a sub-harmonic bunching system to achieve these requirements. The grid will allow controlling the current and eventually feedback on the flattop shape. The gun will operate at 140 kV and an emittance of 14 mm mrad can be obtained. The paper describes the design approach and the results of the systematic electromagnetic simulations to optimize the gun. Care was taken during the mechanical design of the gun to obtain a modular design allowing adjusting for different beam currents and cathode sizes.

TUPP033

Effect of Beam-Loading on the Breakdown Rate of High Gradient Accelerating Structures

499

TUPOL08

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

J.L. Navarro Quirante, R. Corsini, A. Degiovanni, S. Döbert, A. Grudiev, O. Kononenko, G. McMonagle, S.F. Rey, A. Solodko, I. Syratchev, F. Tecker, L. Timeo, B.J. Woolley, X.W. Wu, W. Wuensch
CERN, Geneva, Switzerland
O. Kononenko
SLAC, Menlo Park, California, USA
A. Solodko
JINR, Dubna, Moscow Region, Russia
J. Tagg
National Instruments Switzerland, Ennetbaden, Switzerland
B.J. Woolley
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
X.W. Wu
TUB, Beijing, People's Republic of China

The Compact Linear Collider (CLIC) is a study for a future room temperature electron-positron collider with a maximum center-of-mass energy of 3 TeV. To efficiently achieve such high energy, the project relies on a novel two beam acceleration concept and on high-gradient accelerating structures working at 100 MV/m. In order to meet the luminosity requirements, the break-down rate in these high-field structures has to be kept below 10 per billion. Such gradients and breakdown rates have been demonstrated by high-power RF testing several 12 GHz structures. However, the presence of beam-loading modifies the field distribution for the structure, such that a higher input power is needed in order to achieve the same accelerating gradient as the unloaded case. The potential impact on the break-down rate was never measured before. In this paper we present an experiment located at the CLIC Test Facility CTF3 recently proposed in order to quantify this effect, layout and hardware status, and discuss its first results.

Slides TUPP033 [1.970 MB]

Poster TUPP033 [2.355 MB]

THPP028

Design and Beamloading-Simulations of a Pre-Bunching Cavity for the CLIC Drive Beam Injector

895

SUPG001

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

M. Dayyani Kelisani, S. Döbert, H. Shaker
CERN, Geneva, Switzerland
H. Shaker
IPM, Tehran, Iran

The CLIC project is developing a multi-TeV center-of-mass electron-positron collider based on high-gradient, room-temperature accelerating structures and a novel two-beam RF power generation scheme. The RF power for the CLIC accelerating structures is provided by the so-called drive beam which is a low energy, high current electron beam. The drive beam will be generated from a high current (up to 5 A) pulsed (142μs) thermionic electron gun and then followed by a bunching system. The bunching system is composed of three sub-harmonic bunchers operating at a frequency of 499.75 MHz, a pre-buncher and a traveling wave buncher both operating at 999.5MHz. The pre-buncher cavity, which has a great importance on minimization the satellite population, should be designed with special consideration of the high beam loading effect due to the high current beam crossing the cavity. In this work we report on RF design, analytical beam loading calculations and simulations for the CLIC drive beam injector pre-buncher cavity.

THPP035

Deceleration Measurements of an Electron Beam in the CLIC Test Facility 3

920

SUPG003

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

R.L. Lillestøl, S. Döbert
CERN, Geneva, Switzerland
E. Adli
University of Oslo, Oslo, Norway

The Test Beam Line at the CLIC Test Facility 3 at CERN is a proof-of-principle of the future CLIC decelerators, which will extract a large amount of beam energy for acceleration of the main CLIC beams. The current beamline consists of a FODO lattice with 13 Power Extraction and Transfer Structures (PETS). We discuss beam deceleration measurements of up to 37 %, taking into account effects from the bunch length and the bunch phase. The 12 GHz phase is reproduced based on measurements in a PETS with an uncombined beam. The spectrometer measurements are also compared to predictions based on the beam current and on the produced rf power in the PETS, as well as particle tracking simulations with the Placet code.