[en] The beam-loss-monitors (BLMs) in the HERA-Proton-ring (HERAp) must fulfil the following requirements: They have to measure losses sensitive and fast enough to prevent the superconducting magnets from beam loss induced quenching; the dynamic range of the monitors must exceed several decades in order to measure losses during beam lifetimes of hundreds of hours as well as the much stronger losses that may quench superconducting magnets; they have to be insensitive to the synchrotron radiation of the adjacent electron-ring (HERAe); and their radiation hardness must allow a monitor-lifetime of a few years of HERA operation. These requirements are well satisfied by the HERAp-BLM-System. (orig.)

[en] Beam profile (emittance) and beam halo are characteristic properties of high-intensity and high energy beams that might limit the performance of the accelerator. Therefore a reliable measurement and determination of these parameters is most helpful for the understanding, tuning and improvement of the whole accelerator chain to achieve the best (at least the design-) performance. This talk will give an overview over recent instruments used for non-destructive beam profile and halo monitoring and will discuss their limits, experiences and latest improvements. (author)

[en] During the Luminosity upgrade of HERA in 2000/2001 more than 50 new magnets were installed close to the interaction region to provide a stronger focussing of the two beams. Some of these magnets are located at very large values of the betatron function and therefore can act with a large gain on the beam. Sudden changes in the power supply currents generated very fast beam losses, creating quenches and increased radiation levels. This talk will discuss the improvements made to the HERA machine protection system to make sure that the beam is dumped in time in case of these events. (author)

[en] The first ionisation profile monitor (IPM) at DESY was installed at the end of 1988. Extended versions of the IPM with amplifications from micro channels plates (MCP) were installed in PETRA II in 1989 and in HERA in 1991. These nondestructive monitors are working in vacuum conditions better than 10^-8 mbar. Profiles are acquired at beam energies between 50 MeV and 480 GeV and current from 0.01 μA to 70 mA. The spatial resolution has been studied and is described in detail. Readout is performed using phosphor screens viewed by various video cameras. The continuous video display at the operator console is very useful for beam studies and emittance measurements. (author) 8 refs.; 3 figs

[en] The investigations of radiation damages to Si-PIN-photodiodes are done in view of their applicability as beam loss monitors for the HERA p-ring. The results indicate that photodiodes can withstand doses of 5x10³ Gy without any problems, except a small increase of dark currents. Therefore, these diodes could be used as loss monitors in HERA for several years. (orig.)

[en] The accelerator complex at DESY consists of a number of linear and circular accelerators for acceleration and storage of electrons, positrons and protons. Most of the accelerators are used for the injection scheme of the proton-electron/positron collider HERA. The protons are injected into the proton synchrotron DESY III with a momentum of 310 MeV/c. They are bunched and accelerated to 7.5 GeV/c within 2 s. 8 fills of DESY III can be accumulated in PETRA II, resulting in 70 bunches and a design current of 150 mA. They are accelerated up to 40 GeV/c within 2.5 minutes and injected into HERAp. HERAp can accumulate 200 bunches. The acceleration to 820 GeV/c takes about 30 minutes where the lifetime of the proton beam is a few hundred hours. The electrons/positrons are injected with an energy of 450 MeV from the LINAC II and the intensity accumulator PIA into the electron synchrotron DESY II. They leave the synchrotron with an energy of 7 GeV into PETRA II which accelerates them up to 12 GeV. After injection into HERAe the electrons are accelerated up to 30 GeV and stored for a few hours. The counterrotating electron and proton beams collide head on in three interaction points. To achieve a high luminosity in the HERA ep collider, it is necessary to control the emittance of the proton beam through the entire chain of preaccelerators while the electron beam has its natural emittance. This paper concentrates on the transverse emittance of the proton beam through the chain of proton accelerators DESY III, PETRA II and HERAp. The performance of the profile monitors used in the accelerators is discussed and the different types are compared. Also results of the emittance behavior in the accelerators are presented. (J.P.N.)

[en] The performance of accelerators with high beam power or high stored beam energy is strongly dependent on the way the beam is handled, how beam parameters are measured and how the machine is commissioned. Two corresponding working groups have been organized for the Workshop: group C ''Beam diagnostics, collimation, injection/extraction and targetry'' and group G ''Commissioning strategies and procedures''. It has been realized that the issues to be discussed in these groups are interlaced with the participants involved and interested in the above topics, with an extremely important subject of beam-induced accidents as additional topic. Therefore, we have decided to combine the group sessions as well as this summary report. Status, performance and outstanding issues of each the topic are described in the sections below, with additional observations and proposals by the joint group at the end

[en] For the measurement of the electron beam emittance at the proton-electron storage ring HERA (DESY) a monitor is used which is based on the direct imaging of visible synchrotron radiation from a bending magnet. In order to reduce the thermal heating of the light extracting beryllium mirror it is vertically offset. While the resolution of profile measurements by synchrotron radiation is already strictly limited by fundamental effects, the observation in this off-axis geometry modifies the measured vertical angular intensity distribution leading to an increased contribution of the diffraction limited resolution. In order to describe the resolution broadening effects calculations based on near field computation of synchrotron radiation have been performed with the code SRW. The resulting wavefront has been propagating through the optical elements of the monitor. Taking into account the calculated resolution broadening corrections the deduced beam emittances are in good agreement with the expected design values. (authors)

[en] We have tested the radiation resistance of two 10 cm long CsI (Tl) crystals in the radiation environment of the PETRA e⁺e^- storage ring. The crystals were exposed for 38 days to an average dose of 50 rad and 20 rad, respectively. The exposure lead to a continuous decrease of pulse height with a final reduction of 13 +- 1% (crystal 1 with photodiode readout at 50 rad) and 19.5 +- 2% (crystal 2 with photomultiplier readout at 20 adout at 20 rad). Most of the damage occurred in the first days of exposure. After the end of the exposure we observed a partial recovery of few percent. (orig.)

[en] Light’s linear and circular polarizations are analyzed simultaneously by vector polarimeters mainly in astrophysics. At higher energies Compton scattering or absorption is applied for linear or circular polarization measurements in satellites and accelerators. Here we propose a Compton scattering only vector polarimeter for monitoring photon beams in a non-invasive way. The setup is adjustable to match the initial photons’ energy and can be used for diagnosing electrons’ passage through undulators. In perspective the proposed device could also be explored to measure topological charge of the novel vortex photon beams. (author)