IFMIF-LIPAc Beam Diagnostics. Profiling and Loss Monitoring Systems

IFMIF sera constitué de deux accélérateurs de deutons délivrant des faisceaux continus de 125mA et d énergie 40MeV qui bombarderont une cible de lithium liquide. Face à cette très haute puissance faisceau de 10 MW, de nouveaux défis doivent être relevés pour le développement de tels accélérateurs. C est pour cette raison qu a été prise la décision de construire un accélérateur prototype, LIPAc (Linear IFMIF Prototype Accelerator) ayant les mêmes caractéristiques faisceau qu IFMIF, mais avec une énergie limitée à 9MeV. Dans le cadre de cette thèse, des instruments de diagnostics faisceau ont été développés pour IFMIF et LIPAc. Ces diagnostics concernent des moniteurs de pertes faisceau ainsi que des profileurs transverse de faisceau travaillant en mode intercepteur ou non.Pour la surveillance des pertes faisceau, des chambres à ionisation et des détecteurs au diamant ont été testés et calibrés en neutrons et en g dans la gamme en énergie de LIPAc. Lors de ces expériences, pour la première fois des diamants ont été testés avec succès à des températures cryogéniques. Pour les profileurs interceptant le faisceau, des simulations thermiques ont été réalisées afin d assurer leur bon fonctionnement. Pour les profileurs n interceptant pas le faisceau, des moniteurs basés sur l ionisation du gaz résiduel (IPM) contenu dans le tube faisceau ont été développés. Un prototype a été construit et testé, puis s inspirant de ce retour d expérience les IPMs finals ont été conçus et construits. Pour contrecarrer la charge d espace générée par le faisceau, un algorithme a été élaboré afin de reconstruire le profil réel du faisceau.The IFMIF accelerator will accelerate two 125mA continuous wave (cw) deuteron beams up to 40MeV and blasts them onto a liquid lithium target to release neutrons. The very high beam power of 10MW pose unprecedented challenges for the accelerator development. Therefore, it was decided to build a prototype accelerator, the Linear IFMIF Prototype Accelerator (LIPAc), which has the very same beam characteristic, but is limited to 9 MeV only. In the frame of this thesis, diagnostics devices for IFMIF and LIPAc have been developed. The diagnostics devices consist of beam loss monitors and interceptive as well as non-interceptive profile monitors. For the beam loss monitoring system, ionization chambers and diamond detectors have been tested and calibrated for neutron and g radiation in the energy range expected at LIPAc. During these tests, for the first time, diamond detectors were successfully operated at cryogenic temperatures. For the interceptive profilers, thermal simulations were performed to ensure safe operation. For the non-interceptive profiler, Ionization Profile Monitors (IPMs) were developed. A prototype has been built and tested, and based on the findings, the final IPMs were designed and built. To overcome the space charge of accelerator beam, a software algorithm was written to reconstruct the actual beam profile.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Electronics and algorithms for HOM based beam diagnostics

The signals from the Higher Order Mode (HOM) ports on superconducting cavities can be used as beam position monitors and to do survey structure alignment. A HOM-based diagnostic system has been installed to instrument both couplers on each of the 40 cryogenic accelerating structures in the DESY TTF2 Linac. The electronics uses a single stage down conversion form the 1.7 GHz HOM spectral line to a 20MHz IF which has been digitized. The electronics is based on low cost surface mount components suitable for large scale production. The analysis of the HOM data is based on Singular Value Decomposition. The response of the OM modes is calibrated using conventional BPMs

Design of a final focus system for CLIC in the multibunch regime

We present a design for the CLIC #nal focus system which authorizes the stable multi#bunch operation with a 5 mrad crossing#angle. The loss of luminosity is limited to less than 20# in suchaway that crab#crossing cavities may not be required. The main feature of the design is that the vertically focusing #nal quadrupole is split into a 48 mm large bore superconducting quadrupole and a 13.7 mm bore normal conducting one. In that way# the o##axis outgoing beam is de#ected by the #rst quadrupole into the #eld#free region of the second one. CEA#DAPNIA#SEA#97#17 1 Introduction The preceding #nal focus systems for CLIC had been designed for the single bunch op# eration at zero crossing#angle. With the current CLIC parameters# partially recalled in Table 1# 60 bunches separated by 20 cm #0.67 ns# form a bunch train repeated at 511 Hz rate. Toavoid unwanted collisions at multiples of 10 cm distances away on both sides from the IP# it is necessary to include a non#zero crossing#angle. This c..