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Reference : UMR9012-SYLPRA0-034
Workplace : ORSAY
Date of publication : Wednesday, October 13, 2021
Type of Contract : FTC Scientist
Contract Period : 24 months
Expected date of employment : 1 December 2021
Proportion of work : Full time
Remuneration : Between 2743 and 3896 euros gross per month depending on experience
Desired level of education : 5-year university degree
Experience required : Indifferent
The candidate will contribute to the study, installation and operation of the injection line of a multi-turn, high average current, energy recovery linac (ERL) based on superconducting radio frequency technology called PERLE (Powerful Energy Recovery Linac for Experiments). PERLE is designed to validate and explore a wide range of phenomena specific to this type of accelerator in a previously unexplored operational power regime.
In its final configuration, PERLE will deliver a 500 MeV electron beam at an average intensity of 20 mA, accelerated on three passes through superconducting cavities at 801.6 MHz. A Conceptual Design Report (CDR) was published by the PERLE collaboration in 2017  for a 1GeV version.
Unlike circular accelerators, the beam properties in ERLs do not result from a steady state, but are defined by the electron source and the manipulation performed on the electron packet (magnetic optics and accelerating fields) during its transport, especially in the early stages of acceleration, before reaching the relativistic regime and injection into the main loop of the ERL.
The candidate will have the opportunity to work in a high-level international collaboration, coordinated by IJCLab, bringing together partners with expertise in the design and operation of ERLs. Within IJCLab, he/she will be a member of the Accelerator Physics Cluster.
 D. Angal-Kalinin, PERLE: Powerful Energy Recovery Linac for Experiments - Conceptual Design Report, https://arxiv.org/abs/1705.08783
The PERLE injector must be capable of delivering an average beam current of 20 mA at an energy of about 7 MeV, with a standard emittance of less than 6 mm mrad. These parameters defined the design and technological choices made for the injection line. Thus, the beam will be emitted from a DC gun equipped with a photocathode illuminated by laser pulses with the required space-time structure. Longitudinal compression of the beam after generation at the source will be performed using a buncher (copper RF cavity). The acceleration of the beam to the injection energy will be done within a booster operating at a frequency of 801.6 MHz (same frequency as the ERL linacs). It will be composed of 4 to 5 single-cell (or possibly some double-cell) superconducting cavities. The individual control of the cavities in RF amplitude and phase will allow fine tuning of the size and energy of the accelerated beam. Focusing solenoids located between the DC gun and the booster will be used for beam transport and emittance compensation. At the exit of the booster, the beam is guided to the ERL loop via the merger (a magnetic baffle). The characterisation of the beam parameters will be ensured by appropriate diagnostics along the injection line.
The candidate will contribute to the design effort undertaken within the PERLE collaboration, in particular with regard to the injection line which will define the beam properties in the multi-turn ERL. Indeed, the PERLE injector will deliver an average beam current of 20 mA. This implies a high repetition rate electron packet, and also a high charge per packet (500 pC in a few picoseconds of packet duration at a repetition rate of 40.1 MHz). In the injection line, the beam will be subject to a strong space charge effect, with the electron source at a few hundred keV. In particular, the longitudinal space charge will limit the performance of the electron beam in the merger. The applicant will propose longitudinal space charge attenuations in the injection section. One way may be the optimisation of the laser parameters allowing the photoemission of electrons. In order to linearise the longitudinal phase space, the installation of an additional linearisation cavity may also be considered. The attenuation must be appropriate for the injection section and the whole accelerator. To this end, the applicant will verify the resulting beam dynamics with end-to-end simulation tools.
As the design of the injection line components evolves, the candidate will perform additional simulations to optimise the beam transport from the electron source to the Merger outlet and thus ensure a good transfer to the main ERL loop. Several iterations with colleagues in charge of the ERL optical mesh studies are planned in order to perform full "start to end" simulations and to validate its lattice configuration.
The installation and commissioning of the electron source (a DC-Gun) will take place during this post-doc. The candidate will have the opportunity to participate in the set-up and qualification of the DC gun in collaboration with colleagues from CNRS and STFC-Daresbury. He/she will also have the task of defining and operating the appropriate diagnostics to characterise the electron beam in the injection line.
Depending on the candidate's profile, the involvement in the various tasks will be weighted.
- Good knowledge of accelerator physics
- Knowledge of the physics of low energy space charge dominated beams
- Skills in accelerator design and beam dynamics tools such as ASTRA and GPT
- Experience with experimental accelerator work
- Communication and reasoning skills, analysis, synthesis and critical thinking
- Ability to learn and develop skills, flexibility and adaptability, creativity
- Languages: French and/or English (written/oral)
- Autonomy, organisational skills and accountability
One (or more) of these additional skills could be considered as an asset:
- Knowledge of electron beam diagnostics
- Knowledge of RF design and RF simulation tools
- Basic knowledge of semiconductor physics
- Knowledge of high voltage technology
- Knowledge of vacuum technology (preferably high vacuum)
The Irène Joliot-Curie Laboratory of Physics of the 2 Infinites (IJCLab) is a Joint Research Unit (UMR) under the supervision of the CNRS (IN2P3), the University of Paris-Saclay and the University of Paris. The laboratory is located on the campus of the University Paris-Saclay in Orsay. The campus is located 20 km south of Paris and is easily accessible by RER in 35 minutes.
IJCLab. was created in 2020 from the merger of five units (CSNSM, IMNC, IPN, LAL, LPT). The staff is made up of nearly 560 permanent staff (340 engineers, technicians and administrative staff and 220 researchers and teacher-researchers) and about 200 non-permanent staff, including 120 PhD students. The laboratory's research themes are nuclear physics, high-energy physics, theoretical physics, astroparticles, astrophysics and cosmology, particle accelerators, energy and the environment and health. IJCLab has a very large technical capacity (about 280 IT staff) in all the major areas required to design, develop/implement the experimental set-ups necessary for its scientific activity, as well as the design, development and operation of instruments.
The candidate will be integrated into the Physics, Instrumentation and Beam Manipulation (BIMP) team of the Accelerators Pole under the direction of Luc Perrot. He/she will be supervised by Christelle Bruni, researcher of the team and will also participate in the PERLE collaboration, managed by Walid Kaabi.
The BIMP team is composed of 22 people involved in different areas of accelerator design and associated with projects such as FCC, ThomX, MYRRHA, SPIRAL2, MLL-TRAP...
The PERLE project is part of a collaborative effort between CNRS, CERN, Jefferson Lab (JLAB), Budker Institute of Nuclear Physics (BINP-Novosibirsk), STFC-Daresbury, University of Liverpool and Cornell University.
For this position, a collaboration with STFC-Daresbury is foreseen. The focus will be on the installation and commissioning of the Canon DC.
The candidate will publish and communicate research results in peer-reviewed journals and conferences, as well as in the PERLE Technical Design Report (TDR) that the collaboration will publish.
Constraints and risks
No strain, no risk.
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