New HLI-Frontend

The high charge state injector (HochLadungsInjektor HLI) serves mainly the super heavy element research (SHIP, TASCA), which is one of the outstanding projects at GSI. It was commissioned 20 years ago and comprises the first RFQ-IH accelerator built. After some problems related to the RFQ were overcome, it was known as the reliable working horse for the low energy program at GSI for many years.

In the last time the radio frequency quadrupole (RFQ) accelerator limited the operation of the HLI, while at the same time plans to build a new superconducting linac to provide 100% duty cycle operation became concrete. The decision was taken to start a frontend intensity upgrade program for the HLI which comprises:

• a new RFQ with 100% duty factor capability
• a new superconducting 28 GHz MS-ECR ion source and
• a new LEBT to connect the new source to the HLI

The new RFQ has been commissioned in 2010. The main feature of this RFQ will be its continuous wave (cw) operation capability, which will be fully exploited only when the new source will be installed (see below). For the time being this results in a duty cycle raised by a factor of two, limited by other parts of the UNILAC. The following figures show the RFQ structure and some results from the commissioning.

The development of a 28 GHz multipurpose fully superconducting ECR ion source (MS-ECRIS) is an international project which lasts already several years. This source is expected to deliver higher charge states and higher beam currents. Beam intensity directly benefits from higher currents, while most low energy experiments also demand high average intensities, i.e. high duty cycles. This is achieved by highly charged ions, which need less rf power to be accelerated. See below for an outline of the new HLI configuration with the existing CAPRICE ECR ion source and spectrometer, the RFQ-IH-accelerator, the new MS-ECRIS, spectrometer and LEBT.