We report the high-gradient tests results of a novel traveling wave accelerating structure for $\beta =0.3$ based on a novel approach of operating at the first negative spatial harmonic. Accelerating gradients of 50 MV/m and peak electric fields of 160 MV/m were achieved in a single structure consisting of 15 coupled cells during tests at the advanced photon source. This work was performed by RadiaBeam, in collaboration with the Argonne National Laboratory, as a part of a Research and Development Program for the development of an ultrahigh-gradient linear accelerator, the Advanced Compact Carbon Ion Linac, for hadron therapy.

Conventional thermionic microwave and radio frequency (RF) guns can offer high average beam current, which is important for synchrotron light and terahertz (THz) radiation source facilities, as well as for industrial applications. For example, the Advanced Photon Source at Argonne National Laboratory is a national synchrotron-radiation light source research facility that utilizes thermionic RF guns. However, these existing thermionic guns are bulky, difficult to handle and install, easily detuned, very sensitive to thermal expansion, and due for a major upgrade and replacement. In this paper, we present the design of a new, more stable, and reliable gun with optimized electromagnetic performance, improved thermal engineering, and a more robust cathode mounting technique, which is a critical step to improve the performance of existing and future light sources, industrial accelerators, and electron beam-driven THz sources. We will also present a fabricated gun prototype and show results of high-power and beam tests.

The transverse deflecting cavity can be used to transform particle distributions in the 6D phase space, which makes it a promising component in phase space beam diagnostics and beam manipulations. In the Advanced Photon Source (APS) Linac, a LOLA-type traveling wave deflecting cavity was installed for the diagnostics of beam characteristics, such as the bunch length, bunch temporal profile, time-dependent energy spread and slice (time-correlated) transverse emittance. In this paper, this deflecting cavity is modeled and analyzed with the numerical method. The effects of the center cell and coupler cell dimensions on the performance of the whole structure are studied, which shows the coupler cell radius has a dominant effect over the coupler cell length and slot width on the global reflection coefficient and field flatness. Important RF parameters, such as S11, field flatness and phase advance etc., of the LOLA-II cavity in tuning are calculated and discussed. After optimization, the field flatness of the cavity is 2.1%, the phase advance is 119.66° degrees with a standard deviation smaller than 0.5° and the bandwidth is 15.738 MHz when VSWR < 1.1 (i.e. the S11 < −26 dB). Bead-pull measurements and RF conditioning have been also performed and discussed. Finally, the initial cavity commissioning with electron beam of 375 MeV is reported, and compared with simulation.

The significance of p16/Rb tumor suppressor pathway inactivation in T-cell non-Hodgkin's lymphoma (NHL) remains incompletely understood. We used naturally occurring canine NHL to test the hypothesis that p16 inactivation has specific pathologic correlates. Forty-eight samples (22 T-cell NHL and 26 B-cell NHL) were included. As applicable, metaphase- or array-based comparative genomic hybridization, Southern blotting, promoter methylation, and Rb phosphorylation were used to determine the presence, expression, and activity of p16. Fisher's exact test was used to test for significance. Deletion of p16 (or loss of dog chromosome 11) was restricted to high-grade T-cell NHL (lymphoblastic T-cell lymphoma and peripheral T-cell lymphoma, not otherwise specified). These were characterized by a concomitant increase of tumor cells with Rb phosphorylation at canonical CDK4 sites. Rb phosphorylation also was seen in high-grade B-cell NHL (diffuse large B-cell lymphoma and Burkitt-type lymphoma), but in those cases, it appeared to be associated with c-Myc overexpression. The data show that p16 deletion or inactivation occurs almost exclusively in high-grade T-cell NHL; however, alternative pathways can generate functional phenotypes of Rb deficiency in low-grade T-cell NHL and in high-grade B-cell NHL. Both morphologic classification according to World Health Organization criteria and assessment of Rb phosphorylation are prognostically valuable parameters for canine NHL.

The Advanced Photon Source Deflecting Cavity System for producing short X-ray pulses uses two multi-cell, S-band cavities to apply a deflecting voltage to the stored electron beam ahead of an undulator that supports a beamline utilizing picosecond X-rays. Two additional multi-cell cavities are then used to cancel out the perturbation and restore the electron beam to its nominal orbit. The pulsed rf system driving the deflecting cavities is described. Design tradeoffs are discussed with emphasis on topology considerations and digital control loops making use of sampling technology in a manner consistent with the present state of the art.

Abstract The,Advanced ,Photon ,Source ,(APS) particle accumulator ring (PAR) has dual rf systems: a CW-mode fundamental,rf system,(RF1) operating at 9.77 MHz that accumulates multiple linac pulses into a 0.8-ns bunch, and a12, harmonic ,rf (RF12) that compresses ,the bunch length further to 0.34 ns for injection into the booster. The RF12 capture process is critical for optimal performance ofthe PAR. We investigated the effects of beam ,loading during the RF12 capture and bunch ,length compression processes with both spectrum analysis and streak camera imaging. Based on these observations, a new timing scheme,for the RF12 tuner and ,power ,control was implemented, which has substantially improved the performance of the PAR. We report our observation, the new timing scheme, and beam parameters after optimization.

Each of the rf phase detectors in the Advanced Photon Source linac [1] consists of a module that down converts from S-band to 20 MHz followed by an analog I/Q detector. Phase is calculated from one digitized sample per pulse each of I and Q. The resulting data have excellent long-term stability but are noisy enough so that a number of samples must be averaged to get a usable reading. The more recent requirement to support a selfamplified spontaneous emission (SASE) free-electron laser (FEL) has presented the need to accurately resolve the relative phase of a single pulse. We replaced analog detection with digital sampling and replaced internal intermediate frequency (IF) reference oscillators with a lower-noise external oscillator in order to control the two largest components of noise. The implementation of a central, ultra-low-noise reference oscillator and a distribution system capable of maintaining the low phase noise is described, together with the results obtained to date. The principal remaining technical issue is determining the processing power required as a function of measurement channels per processor, measured pulse repetition rate, intrapulse data bandwidth, and digital filter characteristics. The options and tradeoffs involved and the present status are discussed.

The Advanced Photon Source (APS) has constructed an injector test stand (ITS) for high-brightness electron beam research. The test stand includes three rf ports with independent phase and power control, beamline supports designed for rapid reconfiguration, and a control and diagnostics system based on the design of the APS linac. The beamline design features a high-resolution electron spectrometer that includes provision for operation as a dispersion-free dogleg, and a rapidly reconfigurable gun-to-spectrometer transport line. Picosecond and nanosecond photocathode drive lasers are available; the room shielding is also adequate for the high average beam powers typically produced by thermionic-cathode rf guns. The initially installed gun is a ballistic-compression gun, which requires all three rf ports to be connected to the gun. Plans include the installation of a higher-order mode photoinjector, requiring one rf connection; this will free the other ports to provide power to a small TW linac section and deflector cavity for bunch-length measurements. The test stand is also capable of being used as an operator training facility, and serves as a validation facility and test bed for the APS main injector rf guns.

In the Advanced Photon Source linac gun test area at Argonne National Laboratory a new S-band ballistic bunch compression (BBC) gun is being tested. It was determined that a WR 284 waveguide bidirectional coupler with a directivity of greater than 30 dB and a coupling of -57 /spl plusmn/ 1 dB was desired for evaluation of waveguide rf power conditions. Numerical simulations were performed using the High Frequency Structure Simulator (HFSS) and experimental models were built to determine the optimal dimensions of the bidirectional coupler assembly and the orientation of the loop coupler element. Magnetic and electric fields in the coupler were adjusted by modifying the coupling of the fields as well as the capacitance of the coupling loop.

The high-power S-band switching system for the Advanced Photon Source (APS) linear accelerator (linac) provides for a hot spare for two of the four S-band transmitters. The system utilizes four-port S-band switches of aluminum construction that are pressurized with sulfur hexafluoride during normal operation and are commercially available. A high-power S-band transmitter test stand at the APS linac has shown that processes that include the hand working and electropolishing of sharp edges internal to the aluminum construction of these switches have measurably improved power handling characteristics.

The APS linac modulators provide DC pulses to Thales 35/45-MW klystrons. The modulators are pulse forming network (PFN)-type pulsers with EMI 40-kV switch-mode charging supplies. The PFN consists of two 8-cell lines connected in parallel. EEV CX1836A thyratrons are used as discharge switches. The PSpice simulation of the modulators using OrCAD release 9.1 made it possible to find appropriate parameters of RC circuits that reduce high-frequency ringing of the pulse transformer primary voltage. In order to improve pulse top flatness (originally ±3%), new coils were built and installed. The coils allow discrete tuning of pulse waveforms by changing the amount of used turns. The advantage of two parallel-line PFN configurations was also used. An equivalent method using a low-voltage generator was used for PFN fine tuning.

Exponential growth of self-amplified spontaneous emission at 530nm was first experimentally observed at the Advanced Photon Source low-energy undulator test line in December 1999. Since then, further detailed measurements and analysis of the results have been made. Here, we present the measurements and compare these with calculations based on measured electron beam properties and theoretical expectations.

The S-band linear accelerator (linac), which was built to be the electron source and the front end of the Advanced Photon Source (APS) injector, is now also being used to support a low-energy undulator test line (LEUTL) to drive a free-electron laser (FEL). The APS linac system employs five units of pulsed high-power klystrons (35-MW class) as the main rf sources. The matching pulse modulators provide high-voltage pulses running at 280 kV and 300 A with 3.5-μs pulse width and a nominal pulse repetition rate of 30 Hz. The system availability of the entire APS linac during the last run period of calendar year 2000 was estimated to be slightly over 95%. We present a discussion of the reliability and various fault statistics of the klystron-modulator system together with the key features of the system hardware

An S-band linear accelerator is the source of particles and the front end of the Advanced Photon Source injector. In addition, it supports a low-energy undulator test line (LEUTL) and drives a free-electron laser (FEL). A waveguide-switching and distribution system is now under construction. The system configuration was revised to be consistent with the recent change to electron-only operation. There are now six modulator-klystron subsystems, two of which are being configured to act as hot spares for two S-band transmitters each, so that no single failure will prevent injector operation. The two subsystems are also used to support additional LEUTL capabilities and off-line testing. Design considerations for the waveguide-switching subsystem, topology selection, control and protection provisions, high-power test results, and current status are described

The S-band linear accelerator, which was built to be the source of particles and the front end of the Advanced Photon Source injector, is now also being used to support a low-energy undulator test line (LEUTL) and to drive a free-electron laser (FEL). The more severe rf stability requirements of the FEL have resulted in an effort to identify sources of phase and amplitude instability and implement corresponding upgrades to the rf generation chain and the measurement system. Test data and improvements implemented and planned are described