Malte Schwarz

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.

A Coupled RFQ-IH-DTL Cavity for FRANZ: A Challenge for RF Technology and Beam Dynamics

For the ‘Frankfurt Neutron Source at the Stern-GerlachZentrum’ (FRANZ) facility an inductively coupled combination of a 4-Rod-type Radio-Frequency-Quadrupole (4Rod-RFQ) and an 8 gap interdigital H-type (IH-DTL) structure will provide the main acceleration of an intense proton beam from 120 keV to 2.0 MeV. The RFQ-IH combination with a total length of about 2.3 m will be operated at 175 MHz in cw mode. The expected total power need is around 200 kW. Due to the internal inductive coupling only one RF amplifier is needed, which significantly reduces the investment costs. At present the RFQ is installed separately in the beam line for conditioning up to the design rf power and for measuring the beam quality behind the RFQ. In parallel, the IH-DTL is rf tuned together with a dummy RFQ outside the FRANZ cave. This paper will present the status of the project with emphasis on key questions like beam dynamics constraints, rf tuning issues and technological challenges resulting from the high thermal load in cw operation.

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.