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Magnetotransport at fields up to 500 mT and LF-noise characteristics are reported for miniature magnetoresistors with ferrite concentrators based on Sn-doped n-InSb/i-GaAs heterostructures grown by MBE. The thickness of the InSb epilayers lie in the range 0.55-1-5 μm giving room temperature mobilities of 2.5-5.5 m 2 V - 1 s - 1 with carrier densities of (0.5-1.5) x 10 1 7 cm - 3 . The room temperature magnetoresistance (MR) for our two terminal devices could be as high as 115% at 50 mT which is comparable to the extraordinary MR (ExMR) recently reported in microscopic composite van der Pauw disks four terminal devices [Science 289 (2000) 1530]. In addition, a high signal-to-noise ratio and a good temperature stability of R(B)/R 0 = 0.5-0.83% K - 1 was observed for B < 60 mT (below the saturation field Brat for ferrite). Device resistance stability R 0 (T) was equal to 0.27-0.66% K - 1 in zero field with a nominal device resistance R 0 = 197-224 Ω for DC currents in the range I = 0.01-1.0 mA. The minimum detectable magnetic field is estimated from the reduced differential MR (∂R/∂B)/R = 2000% T - 1 at B = 31 mT and normalised 1/f current noise power spectral density measured at the same field. The resolution limit B m i n = 2.6 nT at 10 2 Hz and B m i n = 0.82 nT at 10 3 Hz. These resolution limits are seven times better than those recently reported for the same material n-InSb/i-GaAs and ferrite fabricated Hall sensors [Magnetotransport and Raman characterization of n-InSb/i-GaAs epilayers, for Hall sensors applications over extremely wide ranges of temperature and magnetic field, Proceedings NGS 10, IPAP Conference Series 2, IPAP, Tokyo, 2001, pp. 151-154].

For the first time, to verify the origin of LF-noise (LFN) in the access resistance of metamorphic SiGe HMOS FETs, we used a thin film n-InSb magnetoresistor (MR) as a reference control. Hybrid MRs were fabricated on NiO×Fe2O3 ferrite substrates from Sn-doped MBE-grown n-InSb/i-GaAs heterostructures. The thickness of the InSb epilayers lie in the range 1.0-2.0 µm giving a room-temperature Hall mobilities of µ = 5.5×104 cm2/Vs at a carrier densities of 5×1016 cm-3. The device resistance could be changed by up to 500% in a magnetic field of B=325 mT. LFN spectra were measured at B=0 and 31mT. Results show that the current dependence of the PSD for this MR is described by the Hooge mobility fluctuation model, according to S I /I 2 =S R /R 2 =a H ×µ(eR / fL 2). A simple design for a calibrated noise reference is proposed.

A separated function, variable energy, drift tube linac (DTL) operating in cw mode at 105 MHz is being built for the ISAC radioactive beam facility at TRIUMF. Included in the design are three buncher cavities installed in the first, second and third drift spaces between the five IH tanks. The main requirements of the bunchers are: cw mode, high effective voltage (up to 0.32 MV), large velocity acceptance (1.8-4.1%). The first DTL buncher has been developed at INR and is being tested at TRIUMF. It is a triple gap split-ring RF structure operating at 105 MHz. Signal level measurements give a Q-value of 4300 which is 74% of MAFIA simulation predictions and a resonant frequency within 0.6% of the calculated value. With cooling water flow of 20 l/min the mechanical vibrations were measured to be of the order of 1 /spl mu/m. Although the design parameters are 56 kV gap voltage and 8 kW nominal power, we demonstrated 85 kV and 16 kW respectively with stable operation.

A separated function, variable energy, drift tube linac (DTL) operating in CW mode is being built for the ISAC radioactive beam facility at TRIUMF. Longitudinal focusing is achieved by positioning 105 MHz rebunching cavities immediately upstream of the second, third and fourth IH accelerating tanks. The three devices must operate at a relatively low /spl beta/ (2.3%, 2.7%, 3.3%) and deliver peak effective voltages in CW mode of 0.19, 0.26 and 0.32 MV respectively. In addition the geometry must allow a large voltage dynamic range for the variable energy operation. A three gap cavity has been chosen as a trade-off between velocity acceptance and peak effective voltage. Several cavity geometries have been considered in order to identify the optimal geometry for this application. We present here a summary of the available buncher designs.

The well known interdigital IH structure is now widely used for acceleration of heavy ions in low /spl beta/ range. Using the main idea of the IH cavities-transformation of the transverse RF voltage into a longitudinal accelerating one, but differing in realization of this principle, several RF structures are considered. In comparison with the IH cavities, the proposed versions originally have practically uniform field distribution along beam axis and no problems with end walls. With the small outer tank diameter, the effective shunt impedance is high enough. The design of the structures and preliminary results of optimization are presented.

In the near future the injection system of the proton linac at DESY will be upgraded. Two different types of H/sup -/-sources are operated at DESY. The new rf-driven volume source is free of cesium. On a long-term basis this source is planned to replace the present operating magnetron source. For reasons of reliability of the proton linac and for further developments of ion sources a parallel operation of two sources should be possible at the Alvarez linac. Each source has a separate RFQ to accelerate the ions to an energy of 750 keV. A new transport line with one dipole, 8 quadrupoles and one intermediate buncher was designed to match the beam between both RFQs and the Alvarez linac. The codes COPPOC and TRANSPORT were used to determine the length of the transport line and the parameters of the dipole and the buncher. Because of the high current of 20 mA and above the estimation of the space charge forces is of special interest. The macro-particle-code PARMTRA takes into account the particle-to-particle electric forces among all particles. The properties of the beam line have been studied in connection with the effects on the final beam quality after acceleration with the 50 MeV Alvarez linac.

The proposal of high order mode (HOM) damping using a heavily loaded annular-slot resonant cavity is described in detail and some results are presented. The investigation has shown, that the damper absorbs enough high RF power from the fundamental mode, leading to a reduction in the Q factor. A brief physical consideration and results of calculations have shown that introducing complex impedance termination (RC chain in series) with a simple realization evolves lower power absorption at the fundamental frequency. A reduction in absorbed RF power at low frequencies of 8-9 times is due to an increase in the absolute value of the loading impedance and introduction of the phase shift between the RF current and voltage.

Using a general electrodynamic approach and particular properties of compensated accelerating structures, the effect of distortions in an accelerating field distribution due to RF power losses in surfaces and for beam acceleration is considered. Consideration shows, that for proton linacs of 'meson facility' type (impulsive beam current I/sub b//spl sime/50 mA, acceleration rate U/sub a//spl sim/2/spl divide/6 MV/m) this effect is not important for all accelerating structures known. When the beam current I/sub b//spl sim/100-300 mA and U/sub a//spl sim/1 MV/m (like linacs for accelerator-driven transmutation technologies), in the structures with small group velocity (/spl beta//sub g//spl ap/0.04) significant distortions will arise and the efficiency of the structure for beam acceleration will drop. For structures with a large group velocity (/spl beta//sub g//spl ap/0.4) such effects will arise at a beam current of several amperes.

A set of triple gap split-ring 106.08 MHz bunchers (bunch-rotator for MEBT and three DTL bunchers) was designed, fabricated and tested for the ISAC project at TRIUMF. These four devices operate at low /spl beta/ (1.8%, 2.3%, 2.7% and 3.3%) and deliver the peak effective voltages in cw mode of 0.07, 0.19, 0.26 and 0.32 MV respectively. The shape of drift tubes was optimized to have a maximum transit time factor with the fixed value of electric field at the surface (1.5 value of Kilpatrick's criterion). 3D simulations were done to adjust optimized drift tubes with split-rings to have an operating frequency and to unify dimensions of the cavities. The bunchers were fabricated in INR and successfully tested at full power in TRIUMF. Some features of the design and results of the tests are reported in this paper.

The special code has been developed for numerical simulation of the multipactor discharge during long-time INR activity in the construction of accelerating structures. It simulates the secondary emission electron trajectories at different levels of rf field using a real electromagnetic field distribution (calculated with modern 2D or 3D software) in the cavity that has a complicated boundary shape. Special implementations have been developed for phase stability investigations. The velocity spread of secondary electrons also may be considered. The results of the simulations were compared with experimental data, showing good coincidence. In this report, the methods of simulation, details and realization of the code are described. Examples of applications for discharge simulations in accelerating cavities are also presented.

The RF test of the magnetron-type varactors have shown the proof of principle of this device. A comparison with the other power RF tunable devices, such as ferrite tuners, shows, that the varactor has a response time a few orders of magnitude shorter. In the experiments this time was estimated to be in the order of 10/sup -6/ sec for an operating frequency /spl ap/66 MHz. This feature of the varactor opens new applications of the varactor for a fast modulation (in order of few tens of the working RF period) of the amplitude and the phase of the accelerating voltage in the the RF cavities. Based on results of numerical simulation, different applications of the device for fast control and improvements in the design to reduce response time are considered.

The disk and washer (DAW) accelerating structure /1/ finds its use in a number of new projects (PIGMI, SNQ etc). It composes the main part of the accelerating structure of the meson factory now under construction in the Institute for Nuclear Research (INR), Moscow. It is known /2,3,4/ that the parasitic modes with azimutnal (?) field variations exist at the operating mode region. In this report different methods of the parasitic modes frequency shift are considered. The main attention is given to the resonant methods, Which are the most efficient.

Several methods of the stop-band width ?f evaluation in compensated structures are briefly observed. Simple for practical usage methods, based on dispersion curve behavior in the vicinity of operating mode, are proposed. The methods are preferable for structures with large group velocity. The numerical simulation proved them to provide the high accuracy of ?f determination. The application of the developed methods is given for the DAW structure in the case of proton and electron linear accelerators.

The disk and washer accelerating structure has a great deal to do with high-beta structures progress. The frequencies and electromagnetic fields for modes, which have a different number of azimuthal variations, are calculated to determined the dispersion properties and other characteristics of parasitic modes in a disc and washer accelerating structure. The main attention was given to the accelerating structure of the linear accelerator of the Institute for Nuclear Research (INR) of the USSR Academy of Sciences. Modification of a structure for PIGMI accelerator (LANL, USA) is considered briefly.

The analysis of the transient interaction of the bunched beam with the hybrid modes in the DAW structure of a multi-sectional proton linac is presented. The interaction intensity depends on a frequency spectrum and transverse coupling impedances of the hybrid modes. A frequency spectrum and the transverse impedance of the hybrid modes for accelerating structure with various value of s have been computed and used for numerical simulation of the transient beam behaviour. The frequences and the transverse shunt impedances of some modes are compared with experimental data. The effect of the initial conditions and the tolerances of the accelerating units and focusing lenses on the beam transverse displacement is presented. The paper contains the evaluation of the beam pulse current limit corresponding to a small deterioration of the beam quality.

The tuning of the linear accelerator of the Moscow meson factory is about to be completed. The kaon factory is the next step after the Meson factory. In the proposal for the Moscow kaon factory the linear accelerator of the meson factory is to be used as the injection for the booster. The main ring is filled during the 40-ms flat bottom magnetic field. The main ring accelerates 9.3*10/sup 13/ protons per pulse from 7.5 GeV to 45 GeV during a period. The reset of the field in the main ring takes 30 ms, and thus one cycle is 120 ms long, for a repetition rate of 8.3 Hz. The extender is needed for slow extraction with 100% duty cycle. >