What is an integrable quench?

Inspired by classical results in integrable boundary quantum field theory, we propose a definition of integrable initial states for quantum quenches in lattice models. They are defined as the states which are annihilated by all local conserved charges that are odd under space reflection. We show that this class includes the states which can be related to integrable boundary conditions in an appropriate rotated channel, in loose analogy with the picture in quantum field theory. Furthermore, we provide an efficient method to test integrability of given initial states. We revisit the recent literature of global quenches in several models and show that, in all of the cases where closed-form analytical results could be obtained, the initial state is integrable according to our definition. In the prototypical example of the XXZ spin-s chains we show that integrable states include two-site product states but also larger families of matrix product states with arbitrary bond dimension. We argue that our results could be practically useful for the study of quantum quenches in generic integrable models

The PLC Control System for the RF Upgrade of the Super Proton Synchrotron

During the CERN Long Shutdown 2 (LS2), the 200 MHz main acceleration system of the Super Proton Synchrotron (SPS) is being upgraded. Two cavities will be added to reach a total of six. Each new cavity will be powered by Solid State Power Amplifiers (SSPA) grouped into 16 "towers" of 80 modules each, in total 2560 modules. This paper describes the newly developed control system which uses a master PLC for control and interlock of each cavity and the slave PLC controllers for each of the solid state amplifier towers. The system topology and design choices are discussed. Control and interlocking of all subsystems necessary for the operation of an RF cavity are detailed, and the interaction between the master and slave PLC controllers is outlined. We discuss some preliminary results and performance of the test installation

Upgrade of the Control System for the LHC High Level RF

The acceleration of particles in CERN’s Large Hadron Collider (LHC) is carried out by sixteen superconducting radiofrequency (RF) cavities. Their remote control is taken care of by a complex system which involves heterogeneous equipment and interfaces with a number of different subsystems, such as high voltage power converters, cryogenics, vacuum and access control interlocks. In view of the renovations of the CERN control system planned for the Long Shutdown 2 (LS2), the control software for the RF system recently underwent a complete bottom-up refactoring, in order to dispose of obsolete software and ensure the operation of the system in the long term. The upgraded software has been deployed one year before LS2, and allowed successful operation of the machine. This paper describes the strategy followed in order to commission the system and to guarantee LHC nominal operation after LS2

First Operation for Stochastic Cooling of P-Bars in the CERN AD Using Optical Delay Notch Filter and Plans 2021 Operation

As part of the consolidation of the stochastic coolingsystem of the CERN Antiproton Decelerator a notch filter with optical delay lines has been developed. During the 2018 run of AD a notch filter with optical delay lines for the longitudinal stochastic cooling at 3.5 GeV/c was successfully tested with beam for the first time. The contribution will summarise the hardware implemented including a comparison of the hardware transfer functions of the new system and the original system using a coaxial cable plant for the same purpose. Automatic monitoring of the hardware transfer function being prepared for 2021 will be provided in order to periodically check drifts of the system and send corrections to the control of the system. Integration of this monitoring and feedforward system into the CERN controls environment will be shown

The new 1-18 MHz wideband RF system for the CERN PS Booster

The LHC Injectors Upgrade (LIU) project at CERN prepares the injectors to meet the requirements of the High Luminosity LHC. For protons, it includes the new Linac4, PS Booster (PSB), PS and SPS. Among the major changes concerning the PSB, the extraction energy increase from 1.4 GeV to 2 GeV and the higher beam intensity, made possible by the Linac4 together with the new charge exchange injection system into the PSB (2E13 protons), strongly affect the RF system requirements. To deal with this more demanding beam operation, a new RF system was designed. It is based on modern magnetic alloy loaded cavities driven by solid-state amplifiers. Its wideband frequency response (1 MHz to 18 MHz) covers all the required frequency schemes. This new RF system has been produced in 2017 and 2018; installation is planned during 2019, the first year of Long Shutdown 2 (LS2) and commissioning is foreseen in 2020. Most of the production and testing was outsourced to industry; parts acceptance, cavities assembly and pre-testing was done in-house. A quality assurance plan was established to achieve the required high reliability. This paper describes the procurement, production and testing strategies and methodologies. It also reports the achieved results, system performances and relevant statistics

Commissioning and Operational Experience Gained with the Linac4 RFQ at CERN

The installation of Linac4 has started in 2013 with the 3 MeV Front End, aiming at delivering a fully commissioned 160 MeV H^{−} beam by 2016. During summer 2013 the H^{−} ion source, a clone of the first prototype, and the Low Energy Beam Transport lines have been installed in the Linac4 tunnel followed shortly by the Radiofrequency Quadrupole accelerator (RFQ), operating at the RF frequency of 352.2 MHz and which accelerates the ion beam to the energy of 3 MeV. The RFQ, which had already been commissioned at the 3 MeV Test Stand, was this time driven by a fully digital LLRF system. This paper reports the result of the bead-pull field check performed after the installation in the tunnel, the experience gained during recommissioning and the results of field characterization as a function of the water temperature in the RFQ cooling channels, showing how the accelerating field can be adjusted by simply tuning the different cavity modules

Successful RF and Cryogenic Tests of the SOLEIL Cryomodule

In the Storage Ring (SR) of the Synchrotron SOLEIL light source, two cryomodules will provide the maximum power of 600 kW required at the nominal energy of 2.75 GeV with the full beam current of 500 mA and all the insertion devices. A cryomodule prototype, housing two 352 MHz superconducting single-cell cavities with strong damping of the Higher Order Modes has been built and successfully tested in the ESRF. Even though the achieved performance (3 MV and 380 kW) does meet the SOLEIL requirement for the first year of operation, it was decided to upgrade the cryomodule prototype before its implementation in the SR. Modifications of the internal cryogenic system as well as the input power and dipolar HOM couplers required complete disassembling, reassembling and testing of the cryomodule, which were carried out at CERN. This refurbishment program, which was achieved in the framework of a collaboration between SOLEIL, CEA and CERN, is reported in this paper. A second cryomodule, similar to the modified prototype, is under manufacturing and will be implemented in the SR by the end of 2006

Status of the HL-LHC Crab Cavity Tuner

The resonance frequency of the HL-LHC Double Quarter Wave (DQW) and Radio Frequency Dipole (RFD) crab cavities is set to the operating frequency of 400.79 MHz by deforming the cavities. For both types of cavities, the tuning principle foresees a symmetric mechanical deformation of parts of the cavities in vertical direction, with the tuner motor placed outside on top of the vacuum vessel. The tuner design was successfully tested on the DQW prototype cryomodule with two cavities in 2018 in the SPS at CERN. This paper describes the design of DQW and RFD crab tuners. The experience and results of assembly and cold testing is given together with some required improvements. Finally, the final series crab tuners preparation is reported

Operation Experience with the LHC ACS RF System

The LHC accelerating RF system consists of two cryomodules per beam, each containing four single-cell niobium sputtered 400.8 MHz superconducting cavities working at 4.5 K and an average accelerating voltage of 2 MV. The paper summarises the experience, availability and evolution of the system within 10 years of operation. The lessons learned from the successful replacement and re-commissioning of one cryomodule with a spare module, and the recent re-test of the originally installed module on the test stand are also included. Finally, a review of currently launched spare cavity production and long-term developments are presented

Status of the SRF systems at HIE-ISOLDE

The HIE-ISOLDE project has been approved by CERN in 2009 and gained momentum after 2011. The final energy goal of the upgrade is to boost the radioactive beams of REX-ISOLDE from the present 3 MeV/u up to 10 MeV/u for A/q up to 4.5. This is to be achieved by means of a new superconducting linac, operating at 101.28 MHz and 4.5 K with independently phased quarter wave resonators (QWR). The QWRs are based on the Nb sputtering on copper technology, pioneered at CERN and developed at INFN-LNL for this cavity shape. Transverse focusing is provided by Nb-Ti superconducting solenoids. The cryomodules hosting the active elements are of the common vacuum type. In this contribution we will report on the recent advancements of the HIE-ISOLDE linac technical systems involving SRF technology. The paper is focused on the cavity production, on the experience with the assembly of the first cryomodule (CM1), and on the results of the first hardware commissioning campaign