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The Super-FRS (Super FRagment Separator) is a part of FAIR (Facility for Antiproton and Ion Research), which will be constructed at GSI, Germany by 17 countries. The Super-FRS comprises 24 superferric dipole magnets. The 2D and 3D magnetic field simulations of the prototype magnet are described in this paper. A passive trim slot and four chamfered removable poles are used to satisfy the required field homogeneity which is better than at 1.6 T, 0.8 T and 0.16 T in a wide elliptical useable aperture of 380 mm 140 mm. Measurement results at various field levels are shown in this paper as well. It can be seen from the comparison of calculation and measurement results that the magnetic designs of the magnet fulfils the requirements.

The future international facility FAIR (Facility for Antiprotons and Ion Research) will deliver beams of all ions up to uranium with intensities of up to 1012 ions/s. At FAIR it will be possible to perform experiments in different fields of physics. A wide range of ions with energies up to 1.5 A GeV will be used for the production of fragments by projectile fragmentation/fission at the in-flight fragment separator, Super-FRS. Rare isotopes of all elements up to uranium will be produced and spatially separated within a few hundred nanoseconds, enabling the study of very short-lived nuclei. The Super-FRS is a large-acceptance device utilizing large-aperture superconducting magnets and employing multiple degrader stages to provide monoisotopic nuclear beams. It serves different experimental branches including a new storage-cooler ring system. Because of high primary beam intensity a challenging design of the target area and the components used in the first dipole stage of the Super-FRS is necessary. These efforts include high-power production targets, beam dumps to catch the remaining primary beam and radiation resistant magnets. In this contribution we present the status of the project.

Investigations of specific heat and T c under pressure are presented for YBa 2 Cu 3 O x (Y123), NdBa 2 Cu 3 O x (Nd123) and Y 1−y Ca y Ba 2 Cu 3 O x (YCa123) for various oxygen contents. In Y123, at the maximum of the specific-heat jump ΔC/T c the pressure dependence of the transition temperature dT c /dp shows a zero crossing. Inversely, at the maximum of dT c /dp the jump in the specific heat becomes minimal. With Ca doping these joint features shift to lower oxygen contents x, whereas Nd123 causes a shift into the opposite direction. Considering the hole doping by Ca and the larger chain fragmentation in Nd123, we rescaled our results with respect to the hole content n h in the CuO 2 planes. In this plot features coalesce in two fixed hole concentrations, n h ≈0.11 and n h 0.17, irrespective of the substitution and doping. The maximum in ΔC/T c may be related to the appearance of a quantum critical point due to the disappearance of a pseudogap for hole contents above n h ≈0.17. The features at n h ≈0.11 point to a drastic change in system properties at this hole content that may be connected to various anomalies found in other properties reported in the literature.

New data on the muon/electron ratio derived from the KASCADE extensive air shower experiment are presented. This ratio is known to be the most sensitive parameter in the determination of the mass of the primary particle when using ground array data. The particle numbers are measured with the KASCADE array comprising 500 m 2 of e/γ- and 620 m 2 of μ - detectors. The primary mass is inferred on an event-by-event basis by comparing the experimental data to corresponding EAS simulations. We observe a change towards a heavier composition with increasing energy above the knee. The sensitivity of this result to the specific hadronic interaction model employed in the simulations (e.g. VENUS and QGSJET) is discussed.

The linear compressibilities and the thermal expansion of an untwined, nearly optimal doped YBa{sub 2}Cu{sub 3}O{sub 6.94} single crystal were measured along the three crystallographic axes with a high-resolution dilatometer mounted in a high-pressure cell. The measurements were performed in a temperature range from 50 K to 320 K under hydrostatic gas pressure of maximal 0.65 GPa. At a temperature of 300 K the measured bulk modulus is reduced and shows a very strong enhancement under increasing pressure due to pressure-induced oxygen ordering. This ordering process can also be related to a glass transition seen in the thermal expansion above 225 K. At lower temperatures, when oxygen ordering is frozen, the bulk modulus is increased and shows a significantly reduced enhancement under pressure. This pressure dependence, however, is still anomalous high, probably caused by bonds of extremely different compressibilities within the unit cell. The widely spread literature data of the bulk modulus can be explained by this high pressure dependence.

Westudied T c of Y Ba 2 Cu 3 O x (Y123), Y 0.89 Ca 0.11 Ba 2 Cu 3 O x (YCa123) and NdBa 2 Cu 3 O x (Nd123) single crystals with various oxygen contents x. Compared to T c (x) of Y123 the T c (x) curves of YCa123 are shifted to lower oxygen contents and the maximum transition temperature T c,max decreases with increasing Ca content whereas in Nd123 T c (x) is shifted to higher oxygen contents and T c,max is increased. According to the universal parabolic T c (n h ) behavior the differences in T c (x) of Y123, YCa123 and Nd123 can be ascribed to different hole concentrations n h in the CuO 2 planes caused by doping via changes in chemistry or structure. In order to study the influence of structural changes on T c we examined the hydrostatic pressure effect dT c /dp (p ≤0.6GPa). In the underdoped region, at n h ≈0.11, the examined compounds show a peak in dT c /dp which is very pronounced for systems with well ordered CuO chains. As this peak occurs at the same n h in all investigated systems it is not caused by oxygen ordering, but its origins might be found in a strong influence of lattice deformations on the electronic structure.

Flat beams feature unequal emittances in the horizontal and vertical phase space. Such beams were created successfully in electron machines by applying effective stand-alone solenoid fringe fields in the electron gun. Extension of this method to ion beams was proposed conceptually. The present paper is on the decoupling capabilities of an ion beam emittance transfer line. The proposed beam line provides a single-knob tool to partition the horizontal and vertical rms emittances, while keeping the product of the two emittances constant as well as the transverse rms Twiss parameters (α_{x,y} and β_{x,y}) in both planes. It is shown that this single knob is the solenoid field strength.

The collector ring is a dedicated ring for fast cooling of ions coming from separators at the FAIR project. To accommodate optimal technical solutions, a structure of a magnet lattice was recently reviewed and modified. Consequently, more appropriate technical solutions for the main magnets could be adopted. A general layout and design of the present machine is shown. The demanding extraction schemes have been detailed and open design issues were completed.

Commensurability effects between vortex distance and crystal lattice constant are investigated by angular dependent magnetization in very pure twinned and twin-free ${\mathrm{NdBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{y}$ single crystals. With increasing temperature the incommensurate states split up and become finally commensurate with half the crystal unit cell. These additional commensurate states are related to a second intrinsic pinning potential within the unit cell or alternatively to a superstructure from distortion of the vortex lattice with respect to the crystal lattice. The role of twins which favor and/or stabilizes the double periodicity is discussed furthermore.

A detector system for directional and time correlation measurements of multiple cosmic muons has been set up within the extensive air shower experiment KASCADE. The system consists of two layers (129 m(2) area each) of position-sensitive multiwire proportional chambers (MWPC) triggered by a layer of segmented plastic scintillation counters placed upon an iron/concrete shielding above the MWPCs. Operation conditions and performance of the MWPCs have been studied by means of a prototype arrangement consisting of a stack of four detectors and two trigger layers. Results of the detailed prototype studies are presented and discussed. In particular, it has been found that for the present purposes an operation with a commonly used argon-methane gas mixture instead of previously used argon-isobutane leads to an excellent performance. The chambers are integrated into the KASCADE experiment as described and are in continuous operation since 1996. Some typical measurements with the full detector assembly are used to illustrate which features of extensive air showers can be studied. (C) 2001 Elsevier Science B.V. All rights reserved.

The Super-FRS will be a large-acceptance two-stage superconducting fragment separator with three exit branches serving different experimental areas. Due to the high primary-beam intensity of up to 1012 ions/s a challenging design of the target area and the components used in the first dipole Super-FRS is necessary. These efforts include high-power production targets, beam-dumps to catch the remaining primary beam, and radiation resistant magnets. In this contribution we summarize the recent developments on these issues.

Superconducting dipole prototype of the Super-FRS (Super FRagment Separator) for FAIR Project (Facility for antiproton and Ion Research) which is jointly developed by the Institute of Modern Physics (Lanzhou), the Institute of Plasma Physics (Hefei) and the Institute of Electrical Engineering (Beijing), have passed the final magnetic field measurement and low temperature test. The magnetic flux density is up to 1.6 T when the operating current is 232 A, and magnetic field homogeneity meets the calculation result which is ±1 × 10-4. The single ramping tests up to 232 A and 278 A at the rate of 3 A/s, 3 triangular cycles ramping up to 232 A within 120 seconds, and the quench tests at 232 A and 278 A by using the spot heater were done. Some other tests were finished at the same time. All the test results indicate that the superconducting dipole prototype could meet the requirements of FAIR.

In YBa 2 Cu 3 O x (x < 7.0), above 225 K a oxygen ordering in the CuO chains is visible as a glass-like transition in thermal-expansion measurements. The large contribution of this process to the thermal expansion and the T c changes observed under application of external hydrostatic pressure point to a strong dependence of the oxygen ordering and its activation energy E a on the unit-cell volume V. If, however, V is changed chemically by replacing Y with other rare earth ions, R, the values of E a reported in the literature show only a slight dependence on V. We have measured the thermal expansion of a YBa 2 Cu 3 O 6.94 single crystal under hydrostatic pressure up to 0.5 GPa. The activation energy at ambient pressure was determined to be 1.0 ± 0.1 eV with a pressure dependence dE a /dp = 78 meV/GPa. The volume dependence dE a /dV = -48 meV/A 3 obtained from these pressure experiments is clearly higher than dE a /dV = -5.4 meV/A 3 from R-ion substitution. Thus we conclude that a non-uniform compression of interatomic distances within the unit cell has to be considered to explain the difference between dE a /dV(p) and dE a /dV(R). The contribution, Δα V , of the ordering process to the thermal-expansion coefficient, α V , increases with pressure, indicating that more and more oxygen atoms take part in the process. From an extrapolation to negative pressure via R-ion substitution we expect a vanishing (R=Nd) or inverted (R=La) pressure effect on oxygen ordering.

In YBa2Cu3Ox, distinct features are found in the pressure dependence of the transition temperature, dTc/dp, and in DeltaCp*Tc, where DeltaCp is the jump in the specific heat at Tc: dTc/dp becomes zero when DeltaCp*Tc is maximal, whereas dTc/dp has a peak at lower oxygen contents where DeltaCp*Tc vanishes. Substituting Nd for Y and doping with Ca leads to a shift of these specific oxygen contents, since oxygen order and hole doping by Ca influences the hole content nh in the CuO2 planes. Calculating nh from the parabolic Tc(nh) behavior, the features coalesce for all samples at nh=0.11 and nh=0.175, irrespective of substitution and doping. Hence, this behavior seems to reflect an intrinsic property of the CuO2 planes. Analyzing our results we obtain different mechanisms in three doping regions: Tc changes in the optimally doped and overdoped region are mainly caused by charge transfer. In the slightly underdoped region an increasing contribution to dTc/dp is obtained when well ordered CuO chain fragments serve as pinning centers for stripes. This behavior is supported by our results on Zn doped NdBa2Cu3Ox and is responsible for the well known dTc/dp peak observed in YBa2Cu3Ox at x=6.7. Going to a hole content below nh=0.11 our results point to a crossover from an underdoped superconductor to a doped antiferromagnet, changing completely the physics of these materials., Comment: 6 pages, 5 figures Proccedings of the 'Stripes 2000' Conference, Rome (2000)