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Dose Measurements of Bremsstrahlung-Produced Neutrons at the Advanced Photon Source

Description: Bremsstrahlung is generated in the storage rings of the synchrotron radiation facilities by the radiative interaction of the circulating particle beam with both the residual gas molecules and storage ring components. These bremsstrahlung photons, having an energy range of zero to the maximum energy of the particle beam, interact with beamline components like beam stops and collimators generating photoneutrons of varying energies. There are three main processes by which photoneutrons may be produced by the high energy bremsstrahlung photons: giant nuclear dipole resonance and decay (10 MeV < E{sub {gamma}} < 30 MeV), quasi-deuteron production and decay (50 MeV < E{sub {gamma}} < 300 MeV), and intranuclear cascade and evaporation (E{sub {gamma}} > 140 MeV). The giant resonance neutrons are emitted almost isotropically and have an average energy of about 2 MeV. High energy neutrons (E > 10 MeV) emitted from the quasi-deuteron decay and intranuclear cascade are peaked in the forward direction. At the Advanced Photon Source (APS), where bremsstrahlung energy can be as high as 7 GeV, production of photoneutrons in varying yields is possible from all of the above three processes. The bremsstrahlung produced along a typical 15.38-m straight path of the insertion device (ID) beamline of the APS has been measured and analyzed in previous studies. High-Z materials constituting the beamline components, such as collimators and beam stops, can produce photoneutrons upon interaction with these bremsstrahlung photons. The 1/E nature of the bremsstrahlung spectrum and the fact that the photoneutron production cross section is comparatively larger in the energy region 10 MeV < E{sub {gamma}} < 30 MeV, results in the giant resonance interaction being the dominant mechanism that generates photoneutrons at the APS. Such neutron flux in the vicinities of the first optics enclosures (FOEs) of ID beamlines is important, from the point of view ...
Date: August 1998
Creator: Job, P. K.; Pisharody, M. & Semones, E.
Partner: UNT Libraries Government Documents Department

Some results of the advanced photon source beam lifetime studies

Description: Total beam lifetime consists of two components: the residual-gas-scattering lifetime and Touschek lifetime. The residual-gas lifetime is comprised of the elastic and inelastic scattering on electrons and elastic and inelastic scattering on nuclei. Touschek scattering involves scattering of particles within the bunch. One usually calculates only the elastic scattering on nuclei (single Coulomb scattering) and inelastic scattering on nuclei (bremsstrahlung) of the residual-gas-scattering lifetime component. Experience gained from computing the beam lifetime in the Advanced Photon Source (APS) storage ring shows that the electron scattering should not be neglected, particularly the inelastic contribution. Given the measured quantities from the APS storage ring, one can compare theoretical predictions with experimental results. Uncertainties in calculating the various contributions to lifetime will be discussed.
Date: June 1, 1997
Creator: Bizek, H.M.
Partner: UNT Libraries Government Documents Department

Particle-beam profiling techniques on the APS storage ring

Description: Characterization of the Advanced Photon Source storage ring particle beams includes transverse and longitudinal profile measurements using synchrotron radiation-based techniques. Both optical (OSR) and x-ray synchrotron radiation stations are now installed. Spatial resolution of about {sigma}=55{mu}m was obtained at low current in the visible field initially. This is expected to improve during commissioning. UV/visible light from the storage ring bending magnet was used to measure the particle beam with a resolution of {sigma}{approximately}80{mu}m and allow operation at 100 mA with the initial x-ray pinhole setup. Early OSR measurements of beam size are consistent with 8.2 nm-rad emittance and 2-3% vertical coupling. Early results with the x-ray pinhole camera are also presented.
Date: December 31, 1996
Creator: Yang, B.X. & Lumpkin, A.H.
Partner: UNT Libraries Government Documents Department

Magnetic measurement data of the 0.8-m prototype quadrupole magnets for the APS storage ring

Description: From magnetic measurement data of the two 0.8-m prototype quadrupole magnets (P-SRQ-1 and P-SRQ-2) and the study of the geometries for the pole-end bevels and pole chamfers, the following conclusions have been made. Mechanical stability of the magnet poles has been achieved by modification of the weld procedures between two quadrants of the magnets. Stability of the magnet-pole positions was measured optically and was also concluded from the fact that the allowed coefficients, mainly sextupole and octupole terms, were independent of the magnet excitation currents. Unallowed multipole field coefficients for the second magnet, without correction of the magnet-pole positions, are smaller than for the first magnet. The field gradient integrals of the two magnets at 400A differ by less than 5 {times} 10{sup {minus}4} for r = 2.5 cm. This indicates that an acceptable magnet assembly procedure has been established. The 2-D calculations and ``body`` measurements for allowed coefficients after the main field, b{sub 5} and b{sub 9}, agree within 1.2 {times} 10{sup {minus}4} at r = 2.5 cm. This implies that the 2-D design geometry is basically correct and acceptable. As expected for a magnet with long and narrow poles, saturation effects of pole shims have been observed. In order to reduce fabrication cost for the end-plates, the geometries for the pole-end bevels and pole chamfers have been studied. By choosing a bevel angle of 61{degree}, instead of 45{degree}, it is possible to have acceptable allowed coefficients with dimensions of pole-chamfers up to 16.5 mm. This allows the design of the end-plate as one piece without removable pole-tip.
Date: July 1, 1995
Creator: Kim, S.H.
Partner: UNT Libraries Government Documents Department

Cornell undulator/summary of discussions

Description: Based on an earlier statement made by CESR (during the meeting in March 1986 at Cornell) that the ring energy can be 6-GeV and the minimum gap can be 0.9 cm, we performed design calculations for the Cornell undulator. These are presented and briefly summaried in this report.
Date: August 5, 1986
Creator: Shenoy, G. & Viccaro, J.
Partner: UNT Libraries Government Documents Department

Survey and alignment report on the primary control network for the APS

Description: During November 1992 the survey and alignment team measured the entire primary control network for the APS. This task had to be finished before the enclosure of the EAA and the RF buildings were put in place, inhibiting several lines of sight necessary for the determination of the monument locations.
Date: February 1, 1993
Creator: Friedsam, H.; Penicka, M. & Zhao, S.
Partner: UNT Libraries Government Documents Department

A positron accumulator ring for APS

Description: The new positron injection scheme is as follows. The cycle rate of the injector synchrotron is increased to 2 Hz. During 0.4 sec of each 0.5-sec synchrotron cycle, 24 linac pulses are injected into the horizontal phase space of the PAR at a 60-Hz rate. Each injected pulse occupies about 1/3 of the circumference of the accumulator ring. After 0.1 sec for longitudinal damping, the single accumulated bunch is transferred into one of the 352.96-MHz buckets of the injector synchrotron RF system. This single bunch is accelerated to 7 GeV and transferred into the storage ring while the PAR accumulates the next bunch of positrons. The injector synchrotron requires only the one high-frequency RF system.
Date: March 1, 1988
Creator: Crosbie, E.A.
Partner: UNT Libraries Government Documents Department

Upgrade opportunities at the Advanced Photon Source made possible by top-up operations.

Description: The default running mode of the storage ring at the Advanced Photon Source is top-up injection with a horizontal emittance of 3.0 nm-rad and a coupling of 2.0%. For a stored current of 100 mA in 23 bunches the lifetime is 7 h. The ability to run in low beam-lifetime conditions gives us the opportunity to make upgrades that would otherwise be futile. Some of the possible upgrade paths are presented here, such as lower emittance and higher-current operation.
Date: June 28, 2002
Creator: Emery, L. & Borland, M.
Partner: UNT Libraries Government Documents Department

High-power Waveguide Dampers for the Short-Pulse X-Ray Project at the Advanced Photon Source

Description: High-power waveguide dampers have been designed and prototyped for the Short-Pulse X-ray (SPX) cavities at the Advanced Photon Source. The cavities will operate at 2.815 GHz and utilize the TM110 dipole mode. As a result, higher-order (HOM) and lower-order mode (LOM) in-vacuum dampers have been designed to satisfy the demanding broadband damping requirements in the APS storage ring. The SPX single-cell cavity consists of two WR284 waveguides for damping the HOMs and one WR284 waveguide for primarily damping the LOM where up to 2kW will be dissipated in the damping material. The damper designs and high-power experimental results will be discussed in this paper.
Date: July 1, 2012
Creator: Waldschmidt, G. J.; Liu, J.; Middendorf, M. E.; Nassiri, A.; Smith, T. L.; Wu, G..= et al.
Partner: UNT Libraries Government Documents Department

Phase loop bandwidth measurements on the advanced photon source 352 MHz rf systems

Description: Phase loop bandwidth tests were performed on the Advanced Photon Source storage ring 352-MHz rf systems. These measurements were made using the HP3563A Control Systems Analyzer, with the rf systems running at 30 kilowatts into each of the storage ring cavities, without stored beam. An electronic phase shifter was used to inject approximately 14 degrees of stimulated phase shift into the low-level rf system, which produced measureable response voltage in the feedback loops without upsetting normal rf system operation. With the PID (proportional-integral-differential) amplifier settings at the values used during accelerator operation, the measurement data revealed that the 3-dB response for the cavity sum and klystron power-phase loops is approximately 7 kHz and 45 kHz, respectively, with the cavities the primary bandwidth-limiting factor in the cavity-sum loop. Data were taken at various PID settings until the loops became unstable. Crosstalk between the two phase loops was measured.
Date: August 1, 1997
Creator: Horan, D.; Nassiri, A. & Schwartz, C.
Partner: UNT Libraries Government Documents Department

APS storage ring vacuum system performance

Description: The Advanced Photon Source (APS) storage ring was designed to operated with 7-GeV, 100-mA positron beam with lifetimes > 20 hours. The lifetime is limited by residual gas scattering and Touschek scattering at this time. Photon-stimulated desorption and microwave power in the rf cavities are the main gas loads. Comparison of actual system gas loads and design calculations will be given. In addition, several special features of the storage ring vacuum system will be presented.
Date: June 1, 1997
Creator: Noonan, J.R.; Gagliano, J. & Goeppner, G.A.
Partner: UNT Libraries Government Documents Department

Reduction of open-loop low frequency beam motion at the APS

Description: The Advanced Photon Source (APS) 7-GeV positron storage ring at Argonne National Laboratory (ANL) produces high brilliance bending magnet and insertion device x-rays for up to 70 x-ray beamlines. To efficiently make use of the storage ring`s high brilliance, an extremely tight tolerance has been placed on positron beam stability, namely that the beam be stable to a level which is less than 5% of its rms size. This requirement amounts to {+-}4.4 microns rms in the vertical plane and {+-}17 microns horizontally, assuming 10% coupling. While real-time closed orbit feedback (discussed elsewhere in these proceedings) will be employed to exceed the required stability requirement, efforts are underway to identify and reduce sources of beam motion in the absence of feedback. These sources include ground- and water-system-induced vibrations in addition to power supply jitter and drift. Results to date of this effort will be presented.
Date: June 1, 1995
Creator: Decker, G.; Kang, Y.G. & Kim, S.
Partner: UNT Libraries Government Documents Department

Alignment and commissionig of the APS beamline front ends

Description: Fifteen out of forty phase-one beamline front ends have been installed in the storage-ring tunnel at the 7-GeV Advanced Photon Source (APS). For the front-end installation, a four-step alignment process was designed and consists of (1) prealigning the front-end components with support tables in the preassembly area, (2) installing the components with tables in the storage-ring tunnel and aligning relative to the APS global telescope survey network, (3) confirming the alignment using a tooling laser alignment system, and (4) performing adjustments with the synchrotron-radiation beam during commissioning. The laser alignment system and the prealignment data- base have been of great importance for the expedient maintenance of front-end components. These tools are very important to a large synchrotron radiation facility such as the APS, since they make a quick alignment setup possible and minimize alignment time inside the tunnel. This paper will present the four-step alignment process, the laser alignment system, and discuss the alignment confirmation results. 6 refs., 5 figs.
Date: December 31, 1995
Creator: Shu, D.; barraza, J.; Ramanathan, M.; Chang, J. & Kuzay, T.M.
Partner: UNT Libraries Government Documents Department

A high-precision pulse-width modulator source.

Description: A novel high-resolution pulse-width modulator (PWM) is being developed for a new digital regulator for the Advanced Photon Source power converters. The circuit features 82-ps setability over an 80-{micro}s range. Our application requires a 50-{micro}s fill-scale range; therefore the 82-ps setability is equivalent to better than 19 bits. The circuit is presently implemented as a VME module and is an integral part of the digital regulator prototype. The design concept and performance results will be presented.
Date: September 30, 1999
Creator: Lenkszus, F. & Laird, R.
Partner: UNT Libraries Government Documents Department

A new hydrostatic leveling system developed for the Advanced Photon Source.

Description: As a result of the calibration tests performed with the first prototype units using the new measurement principle, we believe that the described leveling method is stable and accurate to the micron level with a sufficiently large range for the expected elevation changes of the support girders used in the Advanced Photon Source (APS) storage ring. Although long-term studies with this system have not been conducted, we believe that after installation this system requires little or no servicing for long periods of time. The methods described in this paper cover only the elevation changes of individual vessels. However, changes in the tilt of a girder must also be known. Therefore, a combination of tiltmeters in conjunction with this hydrostatic level system (HLS) would be most suitable for measuring the tilt and elevation changes of the APS girders.
Date: September 18, 1998
Creator: Kivioja, L. A.
Partner: UNT Libraries Government Documents Department