The photoinjector test facility at DESY, Zeuthen site (PITZ), was built to develop and optimize photoelectron sources for superconducting linacs for high-brilliance, short-wavelength free-electron ...laser (FEL) applications like the free-electron laser in Hamburg (FLASH) and the European x-ray free-electron laser (XFEL). In this paper, the detailed characterization of two laser-driven rf guns with different operating conditions is described. One experimental optimization of the beam parameters was performed at an accelerating gradient of about 43 MV=m at the photocathode and the other at about 60 MV=m. In both cases, electron beams with very high phase-space density have been demonstrated at a bunch charge of 1 nC and are compared with corresponding simulations. The rf gun optimized for the lower gradient has surpassed all the FLASH requirements on beam quality and rf parameters (gradient, rf pulse length, repetition rate) and serves as a spare gun for this facility. The rf gun studied with increased accelerating gradient at the cathode produced beams with even higher brightness, yielding the first demonstration of the beam quality required for driving the European XFEL: The geometric mean of the normalized projected rms emittance in the two transverse directions was measured to be 1:26 ` 0:13 mm mrad for a 1-nC electron bunch. When a 10% charge cut is applied excluding electrons from those phase-space regions where the measured phase-space density is below a certain level and which are not expected to contribute to the lasing process, the normalized projected rms emittance is about 0.9 mm mrad.
The Fast Beam Conditions Monitor, BCM1F, in the Compact Muon Solenoid, CMS, experiment was operated since 2008 and delivered invaluable information on the machine induced background in the inner part ...of the CMS detector supporting a safe operation of the inner tracker and high quality data. Due to the shortening of the time between two bunch crossings from 50ns to 25ns and higher expected luminosity at the Large Hadron Collider, LHC, in 2015, BCM1F needed an upgrade to higher bandwidth. In addition, BCM1F is used as an on-line luminometer operated independently of CMS. To match these requirements, the number of single crystal diamond sensors was enhanced from 8 to 24. Each sensor is subdivided into two pads, leading to 48 readout channels. Dedicated fast front-end ASICs were developed in 130nm technology, and the back-end electronics is completely upgraded. An assembled prototype BCM1F detector comprising sensors, a fast front-end ASIC and optical analog readout was studied in a 5GeV electron beam at the DESY-II accelerator. Results on the performance are given.
For undersea cables radiation doses between 2.5 and 25 rad are to be expected during a working life of 25 years. The majority of previous investigations of the radiation sensitivity of optical ...fibers, however, apply dose rates /spl gsim/1 rad/s and total dose values /spl gsim/3/spl times/10/sup 3/ rad. The present paper describes /sup 60/Co irradiations of a Ge-doped single mode fiber with dose rates between 10/sup -4/ and 20 rad/s. Expected loss increase of an undersea optical fiber cable at 1550 nm wavelength with a temperature of 2/spl deg/C is derived by three different methods. The most comfortable and reliable one, the 'dose rate transformation method', yields, for example, a loss of only 0.0244 dB/100 km after 25 years of irradiation with a dose rate of 0.4 rad/s. This method could be the basis of a standard test procedure for the effect of natural radioactivity on optical fibers for very long repeaterless terrestrial and undersea cables.
The radiation sensitivity of type I FBGs written by four different manufacturers with different UV or IR lasers in two different Ge-doped H 2 loaded and unloaded fibers was investigated. The measured ...peak shifts agreed quite well.
Inclusive production of D* mesons in deep-inelastic ep scattering at HERA is studied in the range 5 < Q(2) < 100 GeV2 of the photon virtuality and 0.02 < y < 0.7 of the inelasticity of the scattering ...process. The observed phase space for the D* meson is (pT) (D*) > 1.25 GeV and |eta( D*)| < 1.8. The data sample corresponds to an integrated luminosity of 348 pb(-1) collected with the H1 detector. Single and double differential cross sections are measured and the charm contribution F-2(c (c) over bar) to the proton structure function F-2 is determined. The results are compared to perturbative QCD predictions at next-to-leading order implementing different schemes for the charm mass treatment and with Monte Carlo models based on leading order matrix elements with parton showers.
1. Therapeutic activities for people with dementia have been used to prevent behavior problems, relieve boredom, and to maintain or restore holistic health and function. 2. This study found that ...subjects spent more time actively participating in an activity when they were able to make a cognitive tie between the current activity and an event from their past through reminiscing. 3. Active participation in therapeutic activities was associated with increased daytime napping but was not related to continuous sleep at night.
The influence of additionally injected short-wavelength photobleaching light on the radiation hardness of Ge-doped graded index fibres working at 1300 nm wavelength is investigated. Predictions are ...complicated by the fact that more efficient shortwave bleaching light experiences higher radiation-induced loss. Promising results are found for low fibre temperatures (/spl lsim/-50/spl deg/C) and bleaching light of about 835 nm wavelength.
Influence of radiation damage on BGO scintillation properties Georgii, R.; Meißl, R.; Hajdas, W. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/1998, Letnik:
413, Številka:
1
Journal Article
Recenzirano
Aboard INTEGRAL, the next medium-size γ-ray mission of the European Space Agency (ESA), a high-resolution Ge-spectrometer array with a BGO anticoincidence shield and imaging capability will be flown. ...The influence of the radiation damage on the photoelectron yield of the BGO scintillators due to the radiation environment in the orbit, i.e. γ-rays, electrons and protons from the radiation belts and the cosmic diffuse radiation, was investigated. Irradiation tests with doses equivalent to the orbit conditions were performed and the photoelectron yields of different BGO crystals were measured. It was found that for equal doses the reduction of the photoelectron yield varies strongly for the crystals of different manufacturers. Furthermore, electromagnetic radiation affects the photoelectron yield much stronger than particle radiation. A possible explanation is given by interpreting the effect due to γ-rays primarily as damage of the electronic structure of the BGO, whereas the particle radiation damages mainly the crystal structure.
The production of jets is studied in deep-inelastic e(+) p scattering at low negative four momentum transfer squared 5 < Q(2) < 100 GeV2 and at inelasticity 0.2 < y < 0.7 using data recorded by the ...H1 detector at HERA in the years 1999 and 2000, corresponding to an integrated luminosity of 43.5 pb(-1). Inclusive jet, 2-jet and 3-jet cross sections as well as the ratio of 3-jet to 2-jet cross sections are measured as a function of Q(2) and jet transverse momentum. The 2-jet cross section is also measured as a function of the proton momentum fraction xi. The measurements are well described by perturbative quantum chromodynamics at next-to-leading order corrected for hadronisation effects and are subsequently used to extract the strong coupling as.
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