B1 – Development and Operation

The B1-collaboration is the accelerator working group. Its main tasks are the design, construction, operation and development of particle accelerators, especially the Mainz Microtron facility (MAMI). The worlds only microtron cascade MAMI is delivering an electron beam of outstanding quality. The electron beam produced is continuous wave and has a kinetic energy of up to 1.5 GeV, which is equivalent to 1.5 GV (1 GV = 1 billion volts) of accelerating voltage, and a beam current of 100 µA (= 0.0001 A). These figures give a total beam power of 150 kW. The nearly complete in-house construction of this multi-stage facility has based the high international reputation of the B1-collaboration. Besides the operation of the accelerator, current projects of the B1-working group are among others, an energy upgrade of the existing facility towards 1.6 GeV and the conceptional design of future accelerators dedicated to nuclear physics experiments, e.g. an electron-nucleon collider (ENC) for the upcoming FAIR accelerator complex at GSI Darmstadt. The later is done in close collaboration with the universities of Bonn and Dortmund and the research centre Jülich.


Upgrades & Developments:
To allow for new nuclear physics experiments, the accelerator division is continuously developing and upgrading the existing facility. The basic need for this task is a sound understanding of the accelerator complex, not only from a technical, but even more from the accelerator physical point of view. Thus several beam optical analyses are ongoing, together with conception, design and construction of the diagnostics instrumentation needed. Recent project fields are: improvement of synchrotron radiation monitors for emittance measurements, analysis of longitudinal beam dynamics aiming at an energy regulation system for 1.5 GeV and further technical analysis for the energy upgrade of the microtron cascade.

Future Technologies:
Upcoming nuclear physics experiments arise the need for new concepts of particle acceleration. A promising concept is a superconducting recirculating accelerator for medium energy high current electron beams (i.e. 10 mA at 105 MeV). Since the beam power is rather high (~1 MW), an energy recovering scheme, where the particle beam delivers it's kinetic energy back to the accelerating sections after use with the experimental target, looks promising to decrease the overall power consumption of the accelerator.

The Electron-Nucleon Collider:
In a second conceptual study, the accelerator division collaborates closely with the universities of Bonn and Dortmund and the research centre Jülich on an electron nucleon collider (ENC). This facility is intended to collide 3 GeV polarized electrons with 15 GeV polarized protons and deuterons, respectively. The design is based on the high energy storage ring (HESR) of the FAIR complex at GSI Darmstadt, which will be expanded by a 3 GeV electron accelerator in this concept. Several parameters of both storage rings have to be taken into account and have to be optimized, several subsystems, such as the HESR's electron cooler, have to be upgraded to meet the experimental requirements and are covered within this study.

Research In Accelerator Physics

The accelerator division of the Institute on Nuclear Physics was founded in 1972 by Prof. Dr. H. Herminghaus. The main goal of the group was to develop an accelerator facility for coincidence experiments, since the common experiments were not supposed to lead to any new knowledge. Coincidence experiments demanded a continuous wave particle beam, so traditional pulsed accelerators were not applicable.

In 1976 Herminghaus proposed a race track microtron (RTM 1) as first stage of a planned cascade of three microtrons, which would deliver a particle beam with an energy of up to 855 MeV. The RTM 1 (extraction energy 14 MeV) was completed in 1979; 1983 the RTM 2 delivering 180 MeV was finished (aka MAMI-A) and in 1990 the final 855 MeV stage RTM 3 (MAMI-B) was put into operations in course of a Collaborative Research Centre (CRC 201). The unique MAMI-B was delivering a continuous particle beam of outstanding quality, never reached before in that energy range (transverse emittances at 100 µA: horiz. 8π nmrad, vert. 0.5π nmrad; energy width 13 keV). To reach those figures of merit the formerly used Van-de-Graaf generator was replaced by a radio frequency linear accelerator, which was designed and built in-house. The MAMI-B facility was led by Dr. K.-H. Kaiser until 2005, followed by the current leader Dr. A. Jankowiak, who also supervised the upgrade to MAMI-C.

With the installation of the RTM 3 it was clear, that the concept of the race track microtron had come to a natural end, since any further energy increase would have called for gigantic bending magnets. But already in 1979 a solution was found by Kaiser, that was investigated during the late 1990-ies and led in 1999 to the proposal of the harmonic double-sided microtron (HDSM) at 1.5 GeV as fourth stage (MAMI-C). The HDSM was designed an constructed on-site within the newly founded CRC 443 and also with kind support by the Johannes Gutenberg university Mainz and the federal state of Rhineland-Palatinate. Commissioning of the machine started end of 2006 and since February 2007 and up to now the final stage is routinely operated for nuclear physics experiments.