Installation of a pulsed hydrogen ion stripper

In order to increase the efficiency of ion acceleration, the ions’ charge state is augmented by passing the beam through a medium which strips off several electrons. This process results into a charge state spectrum. Since only one of these charge states is suitable for further acceleration, the spectrum should be as narrow as possible. Its width depends on the stripping media and it turned out that hydrogen gas injected at large pressures, as being applied in the automobile industry, meets bests this requirement.

After successful R&D, such a pulsed hydrogen stripping section shall be installed for regular operation in the UNILAC. This installation must meet several restrictions imposed by safety regulations from explosion protection. Currently, this set-up is planned and first infrastructure has been installed.

Complete 4D Transverse Beam Diagnostics

Projected transverse beam emittances can be considerably enlarged by unwanted inter-plane correlations. These may occur in solenoids, tilted quadrupoles / dipols, or just from beam loss (if the upper left beam edge is lost for instance). As projected emittances are figures of merit for each accelerator, reduction of these emittances is of fundamental interest. Reduction without beam loss can be reached by removing the inter-plane correlations.

However, in order to do so, the correlations must be known. To our knowledge corresponding reliable 4d-diagnostics is not at hand at ion energies exceeding about 150 keV/u.

To overcome this limitation the department developed the 4d-emittance scanner ROSE (ROtierende Strahl-Emittanzmessung). This device comprises a slit/grid emittance measurement unit being installed inside a single rotatable vacuum chamber. Performing emittance scans at different rotation angles gives quantitative access to the inter-plane correlation, hence paving the path towards elimination of the correlations.

The device has been designed, built, and tested in the UNILAC. The results of successfull 4d-measurements are published in Phys. Rev. Accel. Beams 19 072802 (2016)

In 2018 the device and the underlying algorithm were patented. The technology has been transferred to industry and is listed as an example for best practice by the German Ministry of Economics and Climate Protection.


Compression & de-Noising of Large Data Volumes

Analogue to compression and de-noising of data from music or images, physics data can be trimmed. Such data may be more-dimensional maps of mechanical deformation, temperature, material stress, or e.m. field strength. These maps are from measurements or from FEM simulations; hence there are intrinsic noise and errors. Additionally, the data volume is huge.

Major part of the data volume is taken by noise and errors, while the physical essence takes just a minor fraction. Dedicated mathematic algorithms eliminate that noise, thus reducing drastically the data volume, while effectively not changing the essential content.

For instance, an electric field map of an Alvarez-type rf-cavity was reduced in volume by a factor of 10.000 and noise fluctuations have been eliminated.

Dynamics of Coupled Beams, Emittance Tayloring

The department collaborates very closely with the group of Prof. Moses Chung from the POSTECH University (

We aim at improved understanding and application of the dynamics of transversely coupled beams. New methods for the controlled transfer of emittance from one plane into the other were developed (EMTEX) as well as generalization of the Courant-Snyder formalism from two to four dimensions, i.e., from un-coupled to coupled beams.

Linac Operation and Development

During UNILAC operation periods the Department participates to on-call duty services as well as to dedicated machine experiments and developments

LINAC Conference Programme Committee

The Department appoints a member to the LINAC Conference Programme Committee