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The LCLS x-ray free-electron laser at SLAC uses the third km of the original 3-km copper linac. We are now installing LCLS-II, a superconducting linac that replaces the first km. Two undulators, for hard and soft x rays, will be driven by bunches from either linac. One of the solutions developed at SLAC involves a pyroelectric detector, which converts the infrared emitted by the electron bunch into voltage by measuring fast changes in the temperature of the detecting crystal. Not only are the pyrodetectors used at SLAC but also a method with gap diodes. The radial electric field produced by the bunches leaks through a ceramic gap in the beampipe and is collected by a horn antenna and conveyed through a one millimeter waveguide. The waveguides act as a filter, only passing shorter wavelengths and a zero-bias Schottky diode measures the power. In both methods, a portion of the spectral energy emitted by the bunch is intercepted. After normalizing to differentiate between bunches of the same length with different charge, the detected signal is sensitive to only changes in bunch length. This poster discusses the mechanics and optics behind the LCLS-II bunch length monitors operations and plans for collaboration., Proceedings of the 10th International Beam Instrumentation Conference, IBIC2021, Pohang, Rep. of Korea

One of the primary diagnostic tools for beam emittance measurement at the Linac Coherent Light Source II (LCLS-II), an upgrade of the SLAC National Accelerator Laboratory’s Linac Coherent Light Source (LCLS) facility, is the wire scanners. LCLS-II’s new Fast Wire Scanner (FWS) is based on a similar mechanical design of linear servo motor with position feedback from an incremental encoder as that for LCLS. With a high repetition rate of up to 1 MHz from the superconducting accelerator of LCLS-II, it is no longer sufficient to use point-to-point EPICS-controlled moves from wire to wire, as continued exposure will damage the wires. The system needs to perform on-the-fly scans, with a single position versus time profile calculated in advance and executed in a single coordinated motion by Aerotech Ensemble motion controller. The new fast wire scanner control system has several advantages over LCLS fast wire scanner controls with the capability to program safety features directly on the drive and integrate machine protection checks on an FPGA. This paper will focus on the software architecture and implementation for LCLS-II Fast Wire Scanners., Proceedings of the 17th International Conference on Accelerator and Large Experimental Physics Control Systems, ICALEPCS2019, New York, NY, USA

SLAC is now installing LCLS-II, a superconducting electron linac driven by continuous RF at 1.3 GHz. The 4-GeV, 120-kW beam has a maximum rate of nearly 1 MHz and can be switched pulse-by-pulse to either of two undulators, to generate hard and soft x rays. Two detector types measure beam losses. Point beam-loss monitors (PBLMs) set limits at critical loss points: septa, beam stoppers and dumps, halo collimators, protection collimators (which normally receive no loss), and zones with weak shielding. PBLMs are generally single-crystal diamond detectors, except at the gun, where a scintillator on a PMT is more sensitive to the low-energy (1 MeV) beam. Long beam-loss monitors (LBLMs) use 200-m lengths of radiation-hard optical fiber, each coupled to a PMT, to capture Cherenkov light from loss showers. LBLMs protect the entire 4-km path from gun to beam dump and locate loss points. In most regions two fibers provide redundancy and view the beam from different angles. Loss signals are integrated with a 500-ms time constant and compared to a threshold; if exceeded, the beam is stopped within 0.2 ms. We report on our extensive tests of the detectors and the front-end signal processing., Proceedings of the 8th International Beam Instrumentation Conference, IBIC2019, Malmö, Sweden

LCLS-II's high beam rate of almost 1MHz and the requirement that several "high-performance" systems (such as MPS, BPM, LLRF, timing etc.) shall resolve individual bunches precludes the use of a traditional software based control system but requires many core services to be implemented in FPGA logic. SLAC has created a comprehensive open-source firmware framework which implements many commonly used blocks (e.g., timing, globally-synchronized fast data buffers, MPS, diagnostic data capture), libraries (Ethernet protocol stack, AXI interconnect, FIFOs, memory etc.) and interfaces (e.g., for timing, diagnostic data etc.) thus providing a versatile platform on top of which powerful high-performance systems can be built and rapidly integrated., Proceedings of the 16th Int. Conf. on Accelerator and Large Experimental Control Systems, ICALEPCS2017, Barcelona, Spain

The LCLS2 is a CW superconducting LINAC driven X-ray free electron laser under construction at SLAC. The high beam rate of up to 1MHz, and ability to deliver electrons to multiple undulators and beam dumps, results in a beam diagnostics and control system that requires real time data processing in programmable logic. The SLAC Technical Innovation Directorate has developed a common hardware and firmware platform for beam instrumentation based on the ATCA crate format. The FPGAs are located on ATCA carrier cards, front ends and A-D / D-A are on AMC cards that are connected to the carriers by high speed serial JESD links. External communication is through the ATCA backplane, with interlocks and low frequency components on the ATCA RTM. This platform is used for a variety of high speed diagnostics including stripline and cavity BPMs., Proceedings of the 5th Int. Beam Instrumentation Conf., IBIC2016, Barcelona, Spain

SLAC's LCLS-II is a next generation X-ray FEL that will use a CW 4 GeV superconducting linac with nominal bunch spacing of 1us will deliver both soft and hard x-ray FEL to users. In order to achieve the required performance, the SLAC Technical Innovation Directorate has developed a common hardware and firmware platform for beam instrumentation based on the ATCA crate format. We have designed a stripline and cavity BPM system based on this platform that is capable of measuring the beam position at full beam rate. The system will have a dynamic range between 1 pC to 300 pC. This paper will discuss the design of the BPM electronics, overall architecture and performance on LCLS-I., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark