14603783
A Measurement System Using Gp-Ib For A Magnetic Core Test Cavity
In the design of the RF system of the JHF (Japan Hadron Facilit y) proton synchrotrons, it is very important to find a magnetic core to which satisfies the required condition of the JHF accelerators[1]. Ferrite cores are usually used for the magnetic core of the proton synchrotron, however there are some problems. Generally, some ferrite cores have non-linear characteristics which depend on the RF magnetic field. And, there is a size-dependence of the characteristics. Thus, it is required to measure the characteristics of large size magnetic cores. To measure characteristics of the magnetic cores, we have developed a test cavity which is capable of measuring an actual size one, and measurement system using software ‘HP-VEE’[ 2,3] which is possible to control the measurement devices by using a GP-IB command directly. In this measuring system, the acquisition of data and calculation of the characteristics of the magnetic cores are automatically processed.
17428438
Stability analysis using EMTP for JHF systems
The Stability analysis for JHF (Japan Hadron Facility) synchrotron has been performed by using a code for the stability analysis, EMTP(Electronic Magnetic Transient Program). We have examined two cases; a MA (Magnetic Alloy) loaded cavity and ordinary ferrite one. The MA loaded cavity has low Q value and does not require the tuning system for a frequency sweep. The result shows that the MA loaded cavity has larger stable area than the ordinary ferrite loaded cavity. The JHF RF system using the MA loaded cavity can be operated stably. Another simulation has been performed with a code, MC(Micro Cap). The results were consistent with the EMTP analysis.
118377380
Neutron Star Properties in the Chiral Quark–Meson Coupling Model
We study the properties of neutron stars using the chiral quark–meson coupling model, in which the quark–quark hyperfine interaction due to the exchanges of gluon and pion based on chiral symmetry is considered. We also examine the effects of hyperons and Δ-isobars in a neutron star. Extending the SU(6) spin-flavor symmetry to more general SU(3) flavor symmetry in the vector–meson couplings to baryons, the maximum mass of neutron star can reach the recently observed massive pulsar mass, $${1.97 \pm 0.04 M_{\odot}}$$. In this calculation, Λ and Ξ are generated in a neutron star, while Σ and Δ-isobars do not appear.
67769111
Temperature Dependence of the Surface Resistance of Niobium at 1300 MHz - Comparison to BCS Theory -
We have carefully measured the temperature dependence of the surface resistance of three 1300 MHz single cell niobium cavities manufactured from high purity niobium of RRR=200. The cavities had undergone different surface treatment such as BCP, EP, "in-situ" baking at 85 o C and 140 o C, and the data were analyzed by using Halbritter's surface resistance program. Whereas between chemically polished and electropolished surface differences in surface resistance can be explained by mean free path effect, this is no longer true for "in-situ:" 140 o C baked cavities. To explain the data obtained in these tests, additional material parameters such as energy gap and London penetration depth are changing. After an "in-situ" 140 o C baking for app. 40 hrs the BCS surface resistance between 1.8K and 4.3K is lowered by nearly a factor 2 compared to a chemically polished surface. This contribution describes the measurements and attempts to analyze the obtained data.
121917082
New higher-order-mode damping scheme for L-band superconducting cavities using a radial transmission line ☆
For energy recovery linacs, excellent damping of higher-order modes (HOMs) in superconducting cavities is required for preventing beam breakup. As a promising method for this purpose, we propose to damp the HOMs using a radial transmission line attached to the sides of the cavity. The HOM powers are dissipated in RF absorbers while an accelerating field is rejected with a choke filter. An initial design of this radial-line HOM damper was carried out with simulations. Then, we measured the damping of HOMs by means of this method using a model cavity of the TESLA type. Investigations on a single-cell cavity showed a promising performance of HOM damping.
109241787
Test Operation of Ball Screw Type Tuner for Low Loss High Gradient Superconducting Cavity in a Cryomodule
54701295
The first measurement of low-loss 9-cell cavity in a cryomodule at stf
We are constructing Superconducting RF Test Facility (STF) at KEK for the R&D of ILC accelerator. In the beginning of year 2008, we installed one high-gradient Low-Loss (LL) 9-cell cavity into a cryomodule (CM) at STF. We assembled the cavity with an input-coupler and peripherals in a clean room and the cavity package was dressed with thermal shields to be installed in a CM. At the room-temperature, we performed the processing of input-coupler up to the RF power of 350 kW. At the temperatures of 2 K, RF power was supplied from a klystron to the cavity. The lorentz force detuning of cavity was measured and the performance of the cavity packeage was tested. This article presents the results of the first test of the LL 9-cell cavity at 2 K in a CM.