Author: Aulenbacher, K.
Paper Title Page
MOIBCC002
Longitudinal Halo From NEA and PEA Photocathodes  
 
  • M.A. Dehn, K. Aulenbacher, V. Bechthold, F. Fichtner
    IKP, Mainz, Germany
  • K. Aulenbacher
    HIM, Mainz, Germany
 
  Funding: BMBF-HOPE II
For high average electron beam currents the length of the electron bunches must match the acceptance of the accelerator. At Johannes Gutenberg-Universität we are able to measure the longitudinal pulse responses of different photocathodes: negative electron affinity (NEA) types and positive electron affinity (PEA) types. With NEA (Cs:GaAs), the pulse response depends on the wavelength of photoexcitation and show at 800nm a long and relatively intense tail whereas at 400nm a similar shape but with orders of magnitude lower intensity is observed. In comparison to this distribution, PEA pulse responses (K2CsSb) show a similar shape as well but another order of magnitude less intensity than NEA in the blue excitation.
 
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MOPSPP004 Investigation of K2CsSb Photocathodes 4
 
  • V. Bechthold, K. Aulenbacher, M.A. Dehn, S. Friederich
    IKP, Mainz, Germany
  • K. Aulenbacher
    HIM, Mainz, Germany
 
  Funding: BMBF-HOPE II
The interest in multi alkali antimonide photocathodes, e.g. K2CsSb, for future ERL projects like BERLinPro (Berlin Energy Recovery Linac Prototype) and MESA (Mainz Energy-Recovering Superconducting Accelerator) has grown in recent years. In particular for the case of RF-sources the investigation of the time response is of great importance. In Mainz we are able to synthesize these kinds of photocathodes and investigate their pulse response at 1 picosecond level using a radio frequency streak method. We present on the one hand the cathode plant which is used for synthesizing the multi alkali antimonide photocathodes and on the other hand first measurements showing pulse responses of K2CsSb at 400 nm laser wavelength. Furthermore, an analyzing chamber has been installed, which allows investigation of lifetime under laser heating and in-situ measurements of the work function using a UHV Kelvin Probe.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2017-MOPSPP004  
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FRIBCC001 ERL17 Workshop, WG1 Summary: Injectors 77
 
  • E. Wang
    BNL, Upton, Long Island, New York, USA
  • K. Aulenbacher
    HIM, Mainz, Germany
 
  The 59th ICFA Advance Beam Dynamics Workshop on Energy Recovery Linacs, hosted by the CERN was held on CERN campus. The working group (WG) 1 ERL injectors focused on high-brightness, high-power CW electron gun and high QE long lifetime semiconductor photocathode. The working group 1 was separated into two sessions: One is electron gun session, which has eight invited talks; another is photocathode session, which has six invited talks and one contributed talk. This report summarizes the state of the art of electron guns and photocathodes discussed in the ERL workshop WG1.  
slides icon Slides FRIBCC001 [3.229 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2017-FRIBCC001  
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MOPSPP005 The Small Thermalized Electron Source at Mainz (STEAM) 9
 
  • S. Friederich, K. Aulenbacher
    IKP, Mainz, Germany
 
  Funding: Work supported by BMBF-HOPE II and DFG through RTG 2128.
The Small Thermalized Electron Source at Mainz (STEAM) is a photoelectron source which will be operated using NEA GaAs excited near its band gap with an infrared laser wavelength to reach smallest emittances. CST simulations indicate that emittance growth due to vacuum space charge effects can be controlled up to bunch charges of several tens of pC. The goal of the project is to demonstrate that the intrinsical high brightness can still be achieved at such charges. The current status will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2017-MOPSPP005  
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MOPSPP006 SPOCK - a Triode DC Electron Gun With Variable Extraction Gradient 13
 
  • L.M. Hein, K. Aulenbacher, V. Bechthold, M.A. Dehn, S. Friederich, C. Matejcek
    IKP, Mainz, Germany
 
  Funding: German Federal Ministry of Education and Research (BMBF project HOPE-II FKZ 05K16UMA) and the Cluster of Excellence "PRISMA
The electron source concept SPOCK (Short Pulse Source at KPH) is a 100kV DC source design with variable extraction gradient. Due to its triode inspired design the extraction gradient can be reduced for e.g. investigations of cathode physics, but also enhanced to mitigate space charge effects. In the framework of the MESA-Project (Mainz Energy-Recovering Superconducting Accelerator) its design has been further optimized to cope with space charge dominated electron beams. Although it injects its electron beams directly into the LEBT matching section, which excludes any adjustments of the electron spin, the source SPOCK will allow higher bunch charges than the MESA standard source.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2017-MOPSPP006  
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MOPSPP007 Beam Dynamics and Collimation Following MAGIX at MESA 17
 
  • B. Ledroit, K. Aulenbacher
    IKP, Mainz, Germany
 
  Funding: Supported by the DFG through GRK 2128
The Mainz Energy-recovering Superconducting Accelerator (MESA) will be an electron accelerator allowing operation in energy-recovery linac (ERL) mode. After the beam hits the target at the MESA Internal Gas Target Experiment (MAGIX), the beam is phase shifted and recirculated back into the linac sections. These will transfer the kinetic beam energy back to the RF-field by deceleration of the beam and allow for high beam power with low RF-power input. Since most of the beam does not interact with the target, the beam will mostly just pass the target untouched. However, a fraction of the scattered electrons may be in the range outside the accelerator and detector acceptances and therefore cause malicious beam dynamical behavior in the linac sections or even damage to the machine. The goal of this work is to determine the beam behavior upon target passage by simulation and experiment and to protect the machine with a suitable collimation system. The present status of the investigations is presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2017-MOPSPP007  
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MOPSPP008 Low Energy Beam Transport System for MESA 20
 
  • C. Matejcek, K. Aulenbacher, S. Friederich, L.M. Hein
    IKP, Mainz, Germany
 
  An important part of the new accelerator MESA (Mainz Energy recovering Superconducting Accelerator) is the low energy beam transport system connecting the 100 keV electron source with the injector accelerator. Here the spin manipulation and the bunch preparation for the injector accelerator take place. Due to the low energy, space charge will be an challenging issue in this part. Therefore, start-to-end simulations were done with a combination of the two particle dynamics codes PARMELA* and CST**. At the moment, a test setup is being built up to check the functionality of devices and compare the beam parameters with the simulation. Here the focus lies on the bunch preparation system because at this part we expect high impact of the space charge by reason of the necessary bunch compression. The advance of the test setup, the simulations and measurements done so far will be shown.
* Phase and Radial Motion in Ion Linear Accelerators
** Computer Simulation Technology
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2017-MOPSPP008  
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THICCC002 Study of Microbunching Instability in MESA 74
MOPSPP001   use link to see paper's listing under its alternate paper code  
 
  • A. Khan, O. Boine-Frankenheim
    Institut Theorie Elektromagnetischer Felder, TU Darmstadt, Darmstadt, Germany
  • K. Aulenbacher
    IKP, Mainz, Germany
 
  Funding: Supported by the DFG through GRK 2128
The Institute for Nuclear Physics (KPH) at Mainz is building a multi-turn energy recovery linear accelerator, the Mainz Energy-recovering Superconducting Accelerator (MESA), to deliver a CW beam at 105 MeV with short pulses, high current and small emittance for physics experiments with an internal target. Space charge effects potentially cause beam quality degradation for medium energy beams in smaller machines like MESA. As beam quality preservation is a major concern in an ERL during recirculation. We present a study on Microbunching Instability (MBI) caused by Longitudinal Space Charge (LSC) in MESA. Our results demonstrate the impact of the MESA arc lattice design on the development of Microbunching Instability.
 
slides icon Slides THICCC002 [3.365 MB]  
poster icon Poster THICCC002 [1.232 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2017-THICCC002  
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FRIACC002
Nuclear Physics Experiments at Mesa  
 
  • K. Aulenbacher
    IKP, Mainz, Germany
 
  Funding: Work supported by the DFG through excellence cluster PRISMA
The MESA-ERL will create unique possibilities for scattering experiments with windowless targets. This research program will take place at a didicated set up for which a two arm spectrometer with specifically adapted detector technolgy is bein build. The suite of experiemtns includes a wide range of physics topics, e.g. search of exotic particles or accurate determination of nuclear form factors.
 
slides icon Slides FRIACC002 [20.282 MB]  
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