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Coherent pulse stacking (CPS) is a new time-domain coherent addition technique that stacks several optical pulses into a single output pulse, enabling high pulse energy and high average power. A Z-domain model targeting the pulsed laser is assembled to describe the optical interference process. An algorithm, extracting the cavity phase and pulse phases from limited data, where only the pulse intensity is available, is developed to diagnose optical cavity resonators. We also implement the algorithm on the cascaded system of multiple optical cavities, achieving phase errors less than 1.0°(root mean square), which could ensure the stability of CPS.

Coherent pulse stacking (CPS) is a new time-domain coherent addition technique that stacks several optical pulses into a single output pulse, enabling high pulse energy from fiber lasers. We develop a robust, scalable, and distributed digital control system with firmware and software integration for algorithms, to support the CPS application. We model CPS as a digital filter in the Z domain and implement a pulse-pattern-based cavity phase detection algorithm on an field-programmable gate array (FPGA). A two-stage (2+1 cavities) 15-pulse stacking system achieves an 11.0 peak-power enhancement factor. Each optical cavity is fed back at 1.5kHz, and stabilized at an individually-prescribed round-trip phase with 0.7deg and 2.1deg rms phase errors for Stages 1 and 2, respectively. Optical cavity phase control with nanometer accuracy ensures 1.2% intensity stability of the stacked pulse over 12 h. The FPGA-based feedback control system can be scaled to large numbers of optical cavities.

The ALS-U upgrade promises to deliver diffraction limited performance throughout the soft x-ray range by lowering the horizontal emittance to about 50 pm resulting in 2-3 orders of brightness increase for soft x-rays compared to the current ALS. The design utilizes a multi bend achromat lattice with on-axis swap-out injection and an accumulator ring. One central design goal is to install and commission ALS-U within a short dark period. This paper summarizes the status of the conceptual design of the accelerator, as well as some results of the R&D program that has been ongoing for the last 3 years.

In the low-level RF control field, ADC acquisition accuracy and noise set the boundary of our control ability, making it important to develop low-noise acquisition systems. From the design to test stage, all the noise terms should be understood and characterized. The specific need addressed here is the precision acquisition system for the second Linac Coherent Light Source (LCLS-II), led by SLAC National Accelerator Laboratory. Test circuit boards for the LTC2174 and AD9268 ADCs are designed and fabricated by LBNL. An ADC test framework based on FPGA evaluation board to assess performance has been developed. The ADC test framework includes both DSP (Digital Signal Processing) firmware and processing software. It is useful for low-level RF control and other synchronization projects. Investigating the clock jitter between two channels give us an understanding of that noise source. Working with the test framework, the raw ADC data are transferred to a computer through a Gigabit Ethernet interface. Then short-term error signal can be calculated based on a sine wave fit. By changing low-pass filter bandwidth, relative long-term performance can also be obtained. Amplitude jitter and differential phase jitter are the key issues for ADCs. This paper will report the test results for LTC2174 and AD9268 chips. The integral amplitude jitter is smaller than 0.003 %, and the integral phase noise is smaller than 0.0015° (measured at 47 MHz RF, 100 MHz clock, bandwidth 1 Hz to 100 kHz) for both ADC chips.

Improvements in brightness and coherent flux of about two orders of magnitude over operational storage ring based light sources are possible using multi bend achromat lattice designs [1]. These improvements can be implemented as upgrades of existing facilities, like the proposed upgrade of the Advanced Light Source, making use of the existing infrastructure, thereby reducing cost and time needed to reach full scientific productivity on a large number of beamlines. An R&D program was started at LBNL to further develop the technologies necessary for diffraction-limited storage rings. It involves many areas, and focuses on the specific needs of soft x-ray facilities [2]: NEG coating of small chambers, swap-out injection, bunch lengthening, magnets/radiation production, x-ray optics, and beam physics design optimization. Hardware prototypes have been built and concepts and equipment was tested in beam tests on the existing ALS.

The NGLS collaboration is developing design concepts for a multi-beamline soft x-ray FEL array powered by a superconducting linear accelerator, operating with a high bunch repetition rate of approximately 1 MHz. The CW superconducting linear accelerator design is based on developments of TESLA and ILC technology, and is supplied by an injector based on a high-brightness, highrepetition- rate photocathode electron gun. Electron bunches from the linac are distributed by RF deflecting cavities to the array of independently configurable FEL beamlines with nominal bunch rates of ∼100 kHz in each FEL, with uniform pulse spacing, and some FELs capable of operating at the full linac bunch rate. Individual FELs may be configured for different modes of operation, including self-seeded and external-laser-seeded, and each may produce high peak and average brightness x-rays with a flexible pulse format, and with pulse durations ranging from femtoseconds and shorter, to hundreds of femtoseconds. In this paper we describe current design concepts, and progress in RandD activities. Copyright © 2013 CC-BY-3.0 and by the respective authors.

Electron clouds have been shown to trigger fast growing instabilities on proton beams circulating in the SPS [1], and a feedback system to control the instabilities is under active development [2]. We present the latest improvements to the Warp-Posinst simulation framework and feedback model, and its application to the self-consistent simulations of two consecutive bunches interacting with an electron cloud in the SPS.

An x-ray streak camera with high resolution in both temporal and spatial dimensions has been developed. It is achieved by using extraction-mesh acceleration and a large opening aperture magnetic solenoid lens design. High resolutions in the temporal and spatial dimensions can be retained in a wide 53 ps time window. A temporal resolution of 233 fs and a spatial resolution of 10 m have been demonstrated using an Au photocathode.

Bull riders represent a microcosm of athletes in whom severe consequences of femoroacetabular impingement may challenge the limits of arthroscopic intervention. Observations of this cohort may provide meaningful insight into the treatment of other populations. All patients undergoing hip arthroscopy are prospectively assessed with a modified Harris Hip Score. Sixteen consecutive bull riders (21 hips) with minimum 2-year follow-up are reported. The average age was 26 years, duration of symptoms was 33 months, and follow-up was 57 months. Arc of rotational hip motion averaged 31°. All had femoroacetabular impingement (17 combined and 4 cam impingements). Among the cam impingements, 1 also had dysplasia and 1 also had borderline dysplasia. Radiographic Tönnis grades were as follows: 2 Tönnis 1; 18 Tönnis 2; and 1 Tönnis 3. All had acetabular articular damage (14 Outerbridge grade 4; 6 Outerbridge grade 3; and 1 Outerbridge grade 1). Nine underwent microfracture. Four had accompanying femoral chondral lesions (3 grade 3; 1 grade 4). There were 20 labral tears (14 repaired and 6 debrided). All but 1 (95%) improved after surgery. One bilateral case underwent conversion to resurfacing arthroplasty on one side and revision arthroscopy on the other. The average improvement was 21.3 points. Thirteen (81.25%) returned to bull riding at an average of 7 months. Among the 3 who did not return, each had undergone bilateral procedures. There were no complications. Femoroacetabular impingement can be a significant problem among bull riders. Limited range of motion, grade 4 articular damage, and Tönnis 2 radiographic changes may not preclude successful arthroscopic treatment, but advanced bilateral disease may be too much even for these hardened athletes. [Orthopedics. 2024;47(2):79–82.] [ABSTRACT FROM AUTHOR]

The Large Hadron Collider (LHC), presently under construction at CERN, requires monitoring the parasitic charge in the 3.3 ms long gap in the machine fill structure. This gap, referred to as the abort gap, corresponds to the raise time of the abort kickers magnets. Any circulating particle present in the abort gap at the time of the kickers firing is lost inside the ring, rather than in the beam dump, and can potentially damage a number of the LHC components. CERN specifications indicate a linear density of 6 x 106 protons over a 100 ns interval as the maximum charge safely allowed to accumulate in the abort gap at 7 TeV. We present a study of an abort gap monitor, based on a photomultiplier tube with a gated microchannel plate, which would allow for detecting such low charge densities by monitoring the synchrotron radiation emitted in the dedicated diagnostics port. We show results of beam test experiments at the Advanced Light Source (ALS) using a Hamamatsu 5961U MCP-PMT, which indicate that such an instrument has the required sensitivity to meet LHC specifications.