[en] A cryogenic target system for gaseous ⁴He at an operating temperature of 20 K is discussed. Dictated by the experiments, which involve among others recoil particle detection, the target window is made either of Mylar with a thickness of 1.5 μm or Kapton of 7.0 μm. The corresponding upper limits for the working pressure are 25 and 400 kPa, respectively. The heat exchanger can handele up to 10 W of heat dissipated by the electron beam. The maximum value for the luminosity amounts to 2500 μA mg/cm². The effective target thickness which is a function of dissipated beam power can reliably be determinded. (orig.)

[en] Both the injection and extraction line of the Amsterdam Pulse Stretcher ring (AmPS) contain a d.c. septum magnet. The 400 mm long injection septum, located inside the ring vacuum, requires 1075 A in its winding to generate the maximum field of 0.135 T. The 700 mm long extraction septum is outside the vacuum and consists of 2 turns to generate a maximum field of 0.271 T at 2160 A. The injection septum directs the beam parallel to the ring axis by a downward bend. The magnetic extraction septum bends the extracted beam, initially intercepted and separated from the circulating beam by the electrostatic extraction septum. (R.P.) 8 refs.; 5 figs

[en] A polarized ³He internal target was employed at the internal target facility of the Amsterdam electron Pulse Stretcher and Storage ring (AmPS) at the Dutch National Institute for Nuclear and High-Energy Physics (NIKHEF). The unique features of internal targets such as chemical and isotopic purity, high and rapidly reversible polarization, and the ability to manipulate the target spin orientation were successfully demonstrated. A nuclear polarization of 0.50 (0.42) at a ³He gas flow of 1.0 (2.0)x10¹⁷ at s^-1 could be obtained. Operation at a nominal flow of 1x10¹⁷ at s^-1 resulted in a target thickness of 0.7x10¹⁵ at cm^-2 at a target temperature of 17 K

[en] A low-pressure position- and angle-sensitive detector, developed for the detection of low-energy reaction products, emerging from electrodisintegration reactions on few-body nuclei, will be discussed. The detector operates as a low-pressure time projection chamber. A 2 μm aramide foil separates the counting gas (40 mbar isobutane) from the spectrometer vacuum. The position resolution is 0.7 mm, the angular resolution ranges, depending on the kinetic energy of detected particles, from 35 to 65 mrad (FWHM). The efficiency, determined by comparing the yield of elastically scattered electrons off ³He and ⁴He, with that of the recoil nuclei detected in coincidence, is about 70% for 4 to 40 MeV τ-particles. (orig.)

[en] A vertex detector consisting of twelve microstrip gas counters with a total of 24 800 anode strips was constructed for the HERMES experiment at HERA. The active area of the detector equals 137 x 406 mm². It is equipped with a digital readout system. Here, we report on the design of the tracker and the performance during the 1995 running period at the HERMES experiment. (author)

[en] Both the injection and extraction line of the Amsterdam Pulse Stretcher Ring contain a d.c. septum magnet. The 400 mm long injection septum, located inside the ring vacuum requires 1075 A in its winding to generate the maximum field of 0.135 T. The septum thickness at the exit is restricted to 3 mm. The septum is cooled indirectly by using ceramic enamel of 0.2 mm thickness for electrical insulation. Tests at 1 kA in vacuum show a 80degC temperature rise of the winding due to the 300 W dissipation. The heat conductivity of ceramic enamel is at least 0.2 W/m.degC. The stray field is measured to be at maximum 8 Gauss at 850 A. The 700 mm long extraction septum is outside the vacuum and consists of 2 turns to generate a maximum field of 0.271 T at 2160 A. The septum thickness is 5 mm at the entrance. Water cooling is required for the maximum dissipation of 2 kW/m. The mean temperature rise of the windings is measured to be 2.5degC at 1060 A. The maximum integrated stray field at 750 A is measured to be 0.3 mT.m. (author). 8 refs.; 5 figs

[en] Gravity gradient noise generated by seismic displacements may be the limiting factor for the sensitivity of third-generation gravitational wave detectors at frequencies below 10 Hz. A finite element framework has been developed to calculate the soil response to various excitations. The accompanying gravity gradients as a result of the seismic displacement field can then be evaluated. The results of the gravity gradient noise are in good agreement with previous analytical results. Finally results of gravity gradient noise from a single pulse excitation of a homogenous medium are discussed for an underground detector.

[en] A liquid helium target has been developed which allows the detection of low energy charged particles originating from a nuclear reaction in the target over a large angular acceptance (nearly 360deg in the horizontal, and ±50deg in the azimuthal direction). The design, construction and testing of the target is presented. Special care has been taken to construct the target container windows with minimal mass density. The liquid helium, within the region of acceptance of the incident beam, constituted 80% of the complete target mass in the beam leading to low background count rates. The very thin windows (45 mg/cm²) resulted in low thresholds for the detection of charged reaction products. (orig.)

[en] We present a compact, vacuum compatible seismic attenuation system designed to isolate five auxiliary optical benches for Advanced Virgo, a second generation gravitational wave detector. We report on the design of the device, coined MultiSAS (multistage seismic attenuation system) and on its measured vibration isolation performance. The latter can be summarized by quoting a payload isolation ratio at 10 Hz of 100 dB and 140 dB in vertical and horizontal, respectively. We also present the design and performance of the MultiSAS control system along the translation degrees of freedom, as well as a discussion of the possible coupling to the angular degrees of freedom. Over a time-scale of 100 s, 1 m magnitude RMS for translational degrees of freedom is achieved for seismic conditions observed in the past five years at the Virgo site and in Amsterdam. The spectral displacement levels are expected to be lower than 10⁻¹⁴ m from 10 Hz onwards in vertical and horizontal. In addition we discuss effects that could deteriorate the performance of the device such as thermal drifts of the mechanical filters, residual acoustic coupling and cradle effects on the inverted pendulum pre-isolation stage. Mitigation strategies or solutions were devised and installed in the five Advanced Virgo systems. (paper)

[en] We discuss ion extraction from an internal target in a storage ring, separation of atomic and molecular species, and subsequent measurement of the polarization of the atomic ions. This technique can be applied to internal targets of polarized hydrogen, deuterium, ³He and other gases. Here, we report on the development of such a device for a tensor polarized deuterium gas target internal to a medium-energy electron storage ring. Ions were extracted from a storage cell using a spherical deflector and transported to a mass analyzer. In a prototype setup, using electrons from a gun to simulate the electron beam from a storage ring, the tensor polarization of the atomic ions was measured using the ³H(vector d, n)α reaction. The data show that the extraction of ions from a storage-cell target, followed by their mass and polarization analysis, allows the determination of the nuclear polarization of the target independent of its spatial and temporal variations. (orig.)