Abstract
Thanks to the installation of four APPLE X helical undulators, the SASE3 soft X-ray beamline at European XFEL will provide to the experimental stations the polarization control of the ...X-rays. The helical undulators are located downstream with respect to the already existing planar undulators. The design of the magnetic active parts and of the helical undulator support structure requires a new design of the vacuum chamber and its alignment system. This contribution describes the mechanical design, production process, UHV qualification process and alignment of the vacuum chamber.
The European XFEL comprises three undulator systems. All of the systems use standardized mechanical, magnetic and control components. The key elements such as undulators, phase shifters and ...quadrupole movers as well as their controls are described, with special emphasis on the SASE1 undulator system, which was the first to become operational and has been lasing since May 2017. The role of these systems for the commissioning is outlined with special emphasis on beam‐based alignment, which was important to achieve first lasing. Radiation damage was observed. The exposure doses were measured with the online radiation dosimetry system. Countermeasures and latest results are reported, which are important for a high‐duty‐cycle machine such as the European XFEL.
The SASE1 undulator system and its commissioning are described in detail.
The electron linear accelerators driving modern X‐ray free‐electron lasers can emit intense, tunable, quasi‐monochromatic terahertz (THz) transients with peak electric fields of V Å−1 and peak ...magnetic fields in excess of 10 T when a purpose‐built, compact, superconducting THz undulator is implemented. New research avenues such as X‐ray movies of THz‐driven mode‐selective chemistry come into reach by making dual use of the ultra‐short GeV electron bunches, possible by a rather minor extension of the infrastructure.
A rather modest upgrade of the GeV‐level linear accelerator of modern X‐ray free‐electron lasers with purpose‐built THz undulators allows generating intense, tunable and narrow‐bandwidth THz pulses alongside the X‐ray pulses. The enabling technological breakthroughs in accelerator physics are discussed and the arising new research possibilities are presented.
The European X-ray free electron laser (EXFEL) facility is currently under construction 1. Using the principle of self-amplified spontaneous emission (SASE) 2, 3, intense FEL radiation is generated ...in three gap-tuneable undulator systems called SASE1, SASE2, and SASE3. The electron beam energy of the EXFEL is variable between 8.5 and 17.5 GeV. SASE1 and SASE2 are hard X-ray FELs using planar undulators with a period length of 40 mm, called U40s. By a suitable choice of the beam energy and undulator gap, the wavelength can be tuned from 0.05 to 0.4 nm. SASE3 is a soft X-ray FEL using planar undulators with a period length of 68 mm, called U68s. Under the same conditions, the wavelength can be tuned from 0.4 to 5.2 nm.
The Outer Tracker detector of the HERA-B experiment—Part I: Detector Albrecht, H.; Bauer, Th.S.; Beck, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2005, Letnik:
555, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The HERA-B Outer Tracker is a large system of planar drift chambers with about 113
000 read-out channels. Its inner part has been designed to be exposed to a particle flux of up to
2
×
10
5
cm
-
2
s
...-
1
, thus coping with conditions similar to those expected for future hadron collider experiments. Thirteen superlayers, each consisting of two individual chambers, have been assembled and installed in the experiment. The stereo layers inside each chamber are composed of honeycomb drift tube modules with 5 and
10
mm
diameter cells. Chamber aging is prevented by coating the cathode foils with thin layers of copper and gold, together with a proper drift gas choice. Longitudinal wire segmentation is used to limit the occupancy in the most irradiated detector regions to about 20%. The production of 978 modules was distributed among six different laboratories and took 15 months. For all materials in the fiducial region of the detector good compromises of stability versus thickness were found. A closed-loop gas system supplies the Ar/CF
4/CO
2 gas mixture to all chambers. The successful operation of the HERA-B Outer Tracker shows that a large tracker can be efficiently built and safely operated under huge radiation load at a hadron collider.
The HERA-B Outer Tracker is a large detector with 112,674 drift chamber channels. It is exposed to a particle flux of up to
2
×
10
5
cm
-
2
s
-
1
thus coping with conditions similar to those expected ...for the LHC experiments. The front-end readout system, based on the ASD-8 chip and a customized TDC chip, is designed to fulfil the requirements on low noise, high sensitivity, rate tolerance, and high integration density.
The TDC system is based on an ASIC which digitizes the time in bins of about 0.5
ns within a total of 256 bins. The chip also comprises a pipeline to store data from 128 events which is required for a deadtime-free trigger and data acquisition system.
We report on the development, installation, and commissioning of the front-end electronics, including the grounding and noise suppression schemes, and discuss its performance in the HERA-B experiment.
The HERA-B Outer Tracker consists of drift tubes folded from polycarbonate foil and is operated with Ar/CF
4/CO
2 as drift gas. The detector has to stand radiation levels which are similar to LHC ...conditions. The first prototypes exposed to radiation in HERA-B suffered severe radiation damage due to the development of self-sustaining currents (Malter effect). In a subsequent extended R&D program major changes to the original concept for the drift tubes (surface conductivity, drift gas, production materials) have been developed and validated for use in harsh radiation environments. In the test program various aging effects (such as Malter currents, gain loss due to anode aging and etching of the anode gold surface) were observed, and cures by tuning of operation parameters were developed.
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