GeV-Class Two-Fold CW Linac Driven by an Arc-Compressor

Alberto Bacci,Angelo Bosotti,Marcello Rossetti Conti,Laura Monaco,Michele Opromolla,Simone Di Mitri,Illya Drebot,Daniele Sertore,Andrea Renato Rossi,Luca Serafini,Rocco Paparella,Paolo Michelato,Luigi Faillace,Vittoria Petrillo

doi:10.3390/instruments3040054

Alberto Bacci, Angelo Bosotti + Show 12 more

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https://doi.org/10.3390/instruments3040054

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Abstract

We present a study of an innovative scheme to generate high repetition rate (MHz-class) GeV electron beams by adopting a two-pass two-way acceleration in a super-conducting Linac operated in Continuous Wave (CW) mode. The beam is accelerated twice in the Linac by being re-injected, after the first pass, in opposite direction of propagation. The task of recirculating the electron beam is performed by an arc compressor composed by 14 Double Bend Achromat (DBA). In this paper, we study the main issues of the two-fold acceleration scheme, the electron beam quality parameters preservation (emittance, energy spread), together with the bunch compression performance of the arc compressor, aiming to operate an X-ray Free Electron Laser. The requested power to supply the cryogenic plant and the RF sources is also significantly reduced w.r.t a conventional one-pass SC Linac for the same final energy.

Highlights

This paper reports a study on high brightness GeV-class Super Conducting (SC) linear accelerators based on a new scheme named two-pass two-way
The idea of two-way acceleration is not completely new: in Reference [3,4] the concept of beam re-circulation and re-injection for a second pass was proposed; the use of an arc compressor preserving the high brightness of an electron beam was presented in the seminal work in Reference [5], no studies using an arc for both the bunch re-circulation and the bunch compression were already presented from other groups or labs
After the bubble arc compressor (BAC), where the bunch shows a current peak up to 100 times higher, it passes a second time into the qudrupoles matching line, into the SC solenoid and it is accelerated a second time by the SC linac booster in the backward direction overpassing 3 GeV energy

Summary

Introduction

This paper reports a study on high brightness GeV-class Super Conducting (SC) linear accelerators based on a new scheme named two-pass two-way In this scheme a low emittance electron beam, at about 100 MeV, is injected into a SC linac booster, the beam enters an arc compressor that has two objectives: (1) the bunch compression with the low emittance preservation and (2) the beam U-turn that makes it possible to accelerate a second time into the SC linac booster. This two-pass two-way acceleration concept gives the possibility to significantly reduce the machine footprint, as the AC power requirement and adds considerably to the compatibility of such kind of installation with typical university campus layout. The conclusions will focus on the possible outcomes of this innovative acceleration layout

Machine Layout

Start to End Simulation and Results

Findings

Conclusions