67760438
LONG-PERIOD MONITORING OF ELECTRO-POLISHING ELECTROLYTE IN EP FACILITY AT KEK
We have constructed an Electro-polishing (EP) Facility in the Superconducting RF Test Facility (STF) at KEK at the end of 2007. We have begun to operate the EP facility from 2008 and performed the EP processes 41 times with the same EP-electrolyte. In this article, we report the detailed results of the EP-electrolyte monitoring as well as the observation of changing electronic current oscillation in the EP processes. INTRODUCTION In the EP facility, the capacity of the EP-electrolyte reservoir tank is 2,000 L. This size is relatively large if compared with EP facilities in other laboratories. It means that the quality control of EP electrolyte is more difficult because the status of EP-electrolyte changes as the aging of EP-electrolyte proceeds. In the real EP-process operations, we circulated the EP electrolyte of 1,100 L which was firstly delivered into the tank in January 2008 and was disposed in May 2009. During this period, we performed the EP processes 41 times and periodically measured the concentration of Nb, Al, HF in the EP electrolyte. In this article, we report the detailed results of the EP-electrolyte monitoring as well as the observation of changing electronic current oscillation in the EP processes during this period in the EP facility at STF/KEK. [1] [2]. EP PROCESS AT STF-KEK The schematic of EP-electrolyte flow in the EP process is shown in figure 1. The schematic of water flow in the water-rinse process is shown in figure 2, where the process happens just after EP-electrolyte is drained out. The standard EP process at KEK is shown in figure 3, where the flange of cavity is Chemical Polished (CP’ed), the inner surface of cavity is EP’ed, water-rinsed, detergent-rinsed in the ultrasonic hot-water bath, running water-rinsed in hot-water bath, and High-Pressure-Rinsed. Figure 1: Schematic of EP-electrolyte flow. Figure 2: Schematic of water flow in water rinse process. Figure 3: EP process .(EP-2) We performed EP processes 41 times with the first electrolyte from January 2008 to May 2009. The removal weight of Nb in each EP process and summing up of each removal is shown in figure 4. Figure 4: Removal weight in each EP and summing up of each removal. MANAGEMENT OF EP-ELECTROLYTE We measured the concentration of niobium and aluminum in the EP electrolyte by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP) as shown in figure 5. The niobium concentration calculated by current integration (charge) and that of ICP agreed very well. It was found that the concentration of aluminum increases in the similar way to that of niobium. We also measured the fluorine concentration by steam distillation method and Ion Selective Electrode (ISE). All fluorine was measured as in the form of fluorine ion by this method. The picture of the analytical instruments and Proceedings of IPAC’10, Kyoto, Japan WEPEC027 07 Accelerator Technology T07 Superconducting RF 2947 samples of EP-electrolyte are shown in figure 6. We assumed that fluorine in the EP-electrolyte is composed of fluorine in the niobium oxygen complexes (H2NbFO5), in hydrogen fluoride (HF) and in fluorosulfuric acid (SO3F). This assumption was checked by the ion chromatgraph measurements of diluted EP-electrolyte and diluted fluosulfic acid (SO3FH) as shown in figure 7. Because we already measured the niobium concentration in EP-electrolyte by current integration and/or ICP, we can calculate the fluorine quantity in H2NbFO5. On the other hand, the total amont of fluorine is measured by steam distillation method and ISE. Then the sum of fluorine concentration in the form of HF and SO3F can be also calculated by subtracting fluorine in H2NbFO5 from the total fluorine. Figure 5: The changes of niobium and aluminum concentration in the function of days. Figure 6: Analytical instruments and samples of EPelectrolyte. Figure 7: Ion chromatograph of diluted EP-electrolyte and diluted fluorosulfuric acid. Figure 8: The fluorine concentration in the EP-electrolyte as the function of day. The fluorine concentration in the EP-electrolyte as the function of day during the period of one year and six months is shonw in figure 8. It is found that during the period about 16% of fluorine was used for the EP reaction to remove the niobium, and about 20% fluorine moved out from the EP-electrolyte into exhaust gas and rinsed water. MANAGEMENT OF EP-CURRENT We are recording various data in each EP process automatically in the sampling period of one second. We pay special attention to EP current oscillation in them. We compared the shapes of EP current oscillation in last one minute of each EP process. We found that this oscillation pattern changes as the niobium concentration increases as shown in fgure 9. Figure 9: The changes of oscillation pattern with regard to the niobium concentration. The each time-period of all plots is one minute. The EP current is about 250A. We found that the EP current oscillation pattern becomes smoother and the amplitude becomes smaller as the EPelectrolyte aging proceeds, particularly after the niobium concentration of aound 4~5g/L. THE INCOME AND EXPENDITURE OF FLUORINE / NIOBIUM Flow of chemicals in the EP system We performed EP processes 41 times during the period between January 2008 and May 2009. During this perid, we monitored the income and expenditure of chamicals in the EP system. The flow of the chamicals in the EP system is shown in figure 10. The brand-new EPelectrolyte is filled in the EP-tank of the system as income of chamicals. As described in the previous section, the chemicals in the EP-electrolyte escape into the exhast gas and rinsed water. The chemicals in exaust gas are absorbed in the alkaline water of two absorption towers. The alkaline water in two absorption towers was transferred into the waste-water tanks periodically. In the same wate-water tank, the rinsed water of EP processes is drained in. We measured the concentration of fluorine and niobium in waste-water in the same way as the EPelectrolyte. And finally we transferred the aged EPWEPEC027 Proceedings of IPAC’10, Kyoto, Japan 2948 07 Accelerator Technology T07 Superconducting RF electrolyte and waste-water for disposal out of the EP system as shown in figure 10. Figure 10: The flow of the chamicals in the EP system. The income is brand-new EP-electrolyte and the expenditure is aged EP-electrolyte and waste-water. Exhaust gas The exhaust gas is detoxified with two absorption towers, and the detoxified air is discharged in the atmosphere. The two absorption towers are put in series. And alkaline water circulates in the two towers to scrub the exhast gas. The fluorine concentration in alkaline water in each tower was measured periodically. The results of the measurements was that no hydrogen fluorine was found in second tower as shonw in figure 11. This means that the hydrogen fluoride in exhaust gas is completely removed by the two absorption towers. Alkaline absorption water is sent to the waste-water tank regularly. Figure 11: Fluorine concentration in absorption towers. Hydrogen fluoride in exhaust gas is removed completely with No.1 absorption tower. Monitor of income and expenditure The income and expenditure of fluorine/niobium are summarized in table 1, where all numbers are based on the measurements of fluorine and niobium concentrations. The income is composed of the total amount of fluorine in the brand-new EP-electrolyte and the total removal of niobium. The expenditure is composed of flurine and niobium in waste water in eight disposals and aged EPelectrolyte in one disposal. The expenditure of waste water and aged EP-electrolyte can be summed up and compared with the income. The income and expenditure of fluorine/niobium agreed very well. Fluorine of 10,213g in the EP-electrolyte escaped in waste water. This quantity is about 20% of the income. Niobium of 932g moved into the waste water. This quantity is about 10% of all the removal. Table 1: The income and expenditure of EP-electrolyte. INCOME (Electrolyte) Date Carry Volume (l) Fluorine (mg/l) Fluorine (g) Total Removal Weight(g) 2007/12/2 6 1100 49000 53900 9433 EXPENDITURE (Waste Water) Date Carry Volume (l) Fluorine (mg/l) Fluorine (g) Niobium (mg/l) Niobium (g) Disposal 2008/1/11 900 130 117 KEK 2008/2/1 600 350 210 KEK 2008/2/15 900 650 585 KEK 2008/2/29 1000 340 340 KEK 2008/6/19 7500 16
86865953
Present Status of KEKB Vacuum System
The commissioning of KEKB (KEK B-factory) started in December 1998. The vacuum system has been working almost satisfactorily. The photon stimulated gas desorption coefficient of copper beam chamber is decreasing steadily and reached to about 2 - 4 × 10 -6
122032423
Experiences at the KEK B-factory vacuum system
24439340
Direct electron acceleration by stochastic laser fields in the presence of self-generated magnetic fields.
A simple direct acceleration model is proposed, taking into account the stochastic phase disturbance of the coherent driving laser fields. A relativistic single particle simulation shows that plasma electrons are efficiently accelerated far above the ponderomotive energy. The energy and momentum distributions of the accelerated electrons are derived to examine the effects of the self-generated magnetic field on the characteristics of the electron beams. In addition to the beam collimation effect, the magnetic field is found to further enhance the electron acceleration, resulting in the generation of ultrahigh energy electrons.
121897579
Study of timing degradation and light attenuation in long plastic scintillation rods for time-of-flight counters in relativistic heavy ion experiments
Abstract We have studied the timing and light yield characteristics of long and thin scintillator samples of various sizes. Both the light yield and the time resolution degrade exponentially with respect to the distance from one end; the inverse slope parameters for the time resolutions are found to be twice those of the light yield. This is interpreted in terms of a photoelectron statistics picture, which can also explain the observed position dependence of time resolution for time-of-flight counters.
8862999
Recent progress of KEKB
We summarize the machine operation of KEKB during past one year focusing on progress for this period.
120683961
Narrow Spacing Drift Chamber
Linearity and efficiency of a 3-mm spacing drift chamber was examined with an electron beam. A spatial coordinate is measurable with an accuracy of 0.2 mm.
121021517
A honeycomb sandwich structure vacuum jacket for cryogenic targets
Abstract Cryogenic targets (H 2 , D 2 and 4 He) have been built for use in the study of photonuclear reactions with a π sr spectrometer, TAGX, at the 1.3 GeV Tokyo electron synchrotron. A new type of vacuum jacket, fabricated from plastic honeycomb core and Mylar skins, has been used in the target system for more than 5000 hours. The average radiation thickness and the average density of this jacket are measured to be 3.3 × 10 −3 X 0 and 0.15 g/cm 3 , respectively.
118901317
Global Structure and Dynamics of Advection-dominated Accretion Flows around Black Holes
We present global solutions that describe advection-dominated accretion flows around black holes. The solutions are obtained by solving numerically a set of coupled ordinary differential equations corresponding to a steady axisymmetric height-integrated flow. The solutions satisfy consistent boundary conditions at both ends. On the inside, the flow passes through a sonic point and falls supersonically into the black hole with a zero-torque condition at the horizon. On the outside, the flow attaches to a normal thin accretion disk. We obtain consistent transonic solutions for a wide range of values of the viscosity parameter ?, from 0.001 to 0.3. We do not find any need for shocks in our solutions, and we disagree with previous claims that viscous accretion flows with low values of ? must have shocks. We compare the exact global solutions of this paper with a local self-similar solution that has been studied in the past. Although the self-similar solution makes significant errors close to the boundaries, we find that it provides nevertheless a reasonable description of the overall properties of the flow. We compare also two different forms of viscosity: one is based on a diffusion prescription, while the other takes the shear stress to be simply proportional to the pressure. The results with the two prescriptions are similar. We see a qualitative difference between solutions with low values of the visocity parameter, ? 0.01, and those with large values, ? 0.01. The solutions with low ? have their sonic transitions occurring close to the radius of the marginally bound orbit. These flows are characterized by regions of super-Keplerian rotation and have pressure maxima outside the sonic point. The solutions are similar in many respects to the hydrostatic thick tori developed previously as models of active galactic nuclei. In contrast, the solutions with large ? have sonic transitions farther out, close to, or beyond the marginally stable orbit and have no super-Keplerian rotation or pressure maxima. We believe these flows will be nearly quasi-spherical down to the sonic radius and will not have empty funnels along the rotation axis. The large-? solutions are more likely to be representative of real systems, since most observations of astrophysical systems are best fit, within the context of advection-dominated theories, with values of ? 0.1.
14220941
Frequency Correlations of QPOs Based on a Disk Oscillation Model in Warped Disks
In previous papers, we proposed a model that high-frequency quasi-periodic oscillations (QPOs) observed in black-hole and neutron-star X-ray binaries are disk oscillations (inertial-acoustic and/or g-mode oscillations) resonantly excited on warped disks. In this paper we examine whether time variations of the QPOs and their frequenc yc orrelations observed in neutron-star X-ray binaries can be accounted for by this disk-oscillation model. By assuming that a warp has a time-dependent precession, we can well describe the observed frequency correlations among kHz QPOs and low-frequency QPOs over a wide range of frequencies.
42191029
Multipole analysis for absolute magnetic field measured by multi-probe pulsed-NMR method
For accelerator dipole magnets, the study on multipole coefficients in a local region is useful for understanding magnet characteristics and checking construction procedure. The multi-probe pulsed-NMR method is a candidate for measurement of the local multipole coefficients. For the absolute fields measured by the multi-probe pulsed-NMR method, a rigorous application of the Fourier expansion is found to yield multipole coefficients. It is made clear that the direction of the dipole field is unable to be determined by the Fourier expansion alone. For estimating alignment accuracy of pulsed-NMR probes, the relationship between errors of multipole coefficients and those of probe position is derived by the Fourier expansion method. For applying of multi-probe pulsed-NMR method to accelerator dipole magnets, we designed and fabricated a field measuring system using two probes. The probes had NMR coils wound around glass ampoules with a diameter of about 1.4 mm. The NMR signal was processed with a phase lock loop circuit to produce the NMR frequency. Dipole field uniformity and multipole coefficients were measured at 0.35 T for a 1.5 m long dipole magnet. It was confirmed that the field data by this NMR system had an accuracy of 10/sup -6/.