Marco Busch

Conceptual studies of the EUROTRANS front-end

EUROTRANS (EUROpean Research Programme for the TRANSmutation of High Level Nuclear Waste in an Accelerator Driven System) is calling for an efficient high-current CW front-end accelerator system. A combination of RFQ, normal conducting CH- (Crossbar H-mode) and super-conducting CH-DTL which aims to work at 352MHz and accelerate a 30mA proton beam to 17MeV has been studied as a promising candidate. The preliminary conceptual study results are reported with respect to beam dynamics design.

The EUROTRANS Project

Accelerator Driven Systems (ADS) for nuclear waste transmutation require proton drivers with energies between 600 and 800 MeV and beam currents of several mA for demonstrators and up to 25 mA for large industrial systems. Within the EUROTRANS project a 600 MeV linac has been designed to meet the stringent requirements regarding reliability, availability and extreme low beam losses. The first accelerating section using the novel CH‐cavity accelerates the beam to 17 MeV at the injection point into the main linac. The intermediate energy section (17–100 MeV) of the main linac consists of superconducting independently phased spoke‐type cavities followed by the high energy section consisting of 704 MHz superconducting elliptical cavities. The paper covers the development of the linac, prototype testing and reliability considerations of the whole EUROTRANS project.

The superconducting linac approach for IFMIF

The IFMIF project requires a high current D+-linac operated in cw. Due to the cw operation a superconducting linac using CH-structures (see fig. 1) could be an alternative solution compared with the room temperature Alvarez reference design especially with respect to avoiding thermal problems and to reducing the operational costs.

First Heavy Ion Beam Acceleration with a Superconducting Multi Gap CH-cavity

A newly developed superconducting 15-gap RF-cavity has been successfully tested at GSI Helmholtzzentrum für Schwerionenforschung. After a short commissioning and ramp up time of some days, a Crossbar H-cavity accelerated first time heavy ion beams with full transmission up to the design beam energy of 1.85 MeV/u. The design acceleration gain of 3.5 MV inside a length of less than 70 cm has been verified with heavy ion beam of up to 1.5 particle mueA. The measured beam parameters showed excellent beam quality, while a dedicated beam dynamics layout provides beam energy variation between 1.2 and 2.2 MeV/u. The beam commissioning is a milestone of the R&D work of Helmholtz Institute Mainz (HIM) and GSI in collaboration with Goethe University Frankfurt (GUF) towards a superconducting heavy ion continuous wave linear accelerator cw-Linac with variable beam energy. Further linac beam dynamics layout issues will be presented as well.

Advanced Approach for Beam Matching along the Multi-Cavity SC CW Linac at GSI

A multi-stage program for the development of a heavy ion superconducting (sc) continuous wave (cw) linac is in progress at HIM (Mainz, Germany) and GSI (Darmstadt, Germany) under support of IAP (Frankfurt, Germany). In 2017 the first section of the CW-Linac has been successfully commissioned at GSI. Beam acceleration at the CWLinac is foreseen to be performed by twelve multi-gap Crossbar H-type (CH) cavities. The linac should provide the beam for physics experiments, smoothly varying the output particle energy from 3.5 to 7.3 MeV/u, simultaneously keeping high beam quality. Due to a wide variation of the input and output beam energy for each cavity, a longitudinal beam matching to every cavity is of high importance. An advanced algorithm for an optimization of matched beam parameters under variable rf-voltage and rf-phase of each cavity has been developed. The description of the method and the obtained results are presented . INTRODUCTION The design, construction and operation of continuous wave (cw) proton and ion linacs is a crucial goal of worldwide accelerator technology development. Also a high energy cw linac is an essential part of a large scale research facility, as an accelerator driven system or a spallation neutron source [1-3]. A cw linac in the medium energy range could be used for several applications, as high productivity isotope generation, material science and boron-neutron capture therapy. The compactness of such cw facilities, accomplished by the use of superconducting (sc) elements, is a modern trend for the development of high intensity ion linacs [48]. Therefore the elaboration and optimization of a cw linac, as well as progress in elaboration of the superconducting technology, is of high relevance. Figure 1: Conceptual layout of heavy ion superconducting CW-Linac with warm injector.

R&D Status of the New Superconducting CW Heavy Ion LINAC@GSI

To keep the ambitious Super Heavy Element (SHE) physics program at GSI competitive a superconducting (sc) continuous wave (cw) high intensity heavy ion LINAC is currently under progress as a multi-stage R&D program of GSI, HIM and IAP [2]. The baseline linac design consists of a high performance ion source, a new low energy beam transport line, an (cw) upgraded High Charge State Injector (HLI), and a matching line (1.4 MeV/u) which is followed by the new sc-DTL LINAC for post acceleration up to 7.3 MeV/u. In the present design the new cw-heavy ion LINAC comprises constant-beta sc Crossbar-H-mode (CH) cavities operated at 217 MHz. The advantages of the proposed beam dynamics concept applying a constant beta profile are easy manufacturing with minimized costs as well as a straightforward energy variation [6]. An important milestone will be the full performance test of the first CH cavity (Demonstrator), in a horizontal cryo module with beam. An advanced Demonstrator setup comprising a string of cavities and focussing elements is proposed to build from 10 short CH-cavities with 8 gaps. The corresponding simulations and technical layout of the new cw heavy ion LINAC will be presented.