Measurements and calibration of the stripline BPM for the ELI-NP facility with the stretched wire method

A methodology has been developed to perform electrical characterization of the stripline BPMs for the future Gamma Beam System of ELI Nuclear Physics facility in Romania. Several prototype units are extensively benchmarked and the results are presented in this paper. The BPM sensitivity function is determined using a uniquely designed motorized test bench with a stretched wire to measure the BPM response map. Here, the BPM feedthroughs are connected to Libera Brilliance electronics and the wire is fed by continuous wave signal, while the two software-controlled motors provide horizontal and vertical motion of the BPM around the wire. The electrical offset is obtained using S-parameter measurements with a Network Analyzer (via the “Lambertson” method) and is referenced to the mechanical offse

Development and beam tests of an automatic algorithm for alignment of LHC collimators with embedded BPMs

Collimators with embedded Beam Position Monitor (BPM) buttons will be installed in the LHC during the upcoming long shutdown period. During the subsequent operation, the BPMs will allow the collimator jaws to be kept centered around the beam trajectory. In this manner, the best possible beam cleaning efficiency and machine protection can be provided at unprecedented higher beam energies and intensities. A collimator alignment algorithm is proposed to center the jaws automatically around the beam. The algorithm is based on successive approximation, as the BPM measurements are affected by non-linearities, which vary with the distance between opposite buttons, as well as the difference between the beam and the jaw centers. The successful test results, as well as some considerations for eventual operation in the LHC are also presented.peer-reviewe

LHC Impedance Model: Experience with High Intensity Operation in the LHC

The CERN Large Hadron Collider (LHC) is now in luminosity production mode and has been pushing its performance in the past months by increasing the proton beam brightness, the collision energy and the machine availability. As a consequence, collective effects have started to become more and more visible and have effectively slowed down the performance increase of the machine. Among these collective effects, the interaction of brighter LHC bunches with the longitudinal and transverse impedance of the machine has been observed to generate beam induced heating, as well as longitudinal and transverse instabilities since 2010. This contribution reviews the current LHC impedance model obtained from theory, simulations and bench measurements as well as a selection of measured effects with the LHC beam

Update on Beam Induced RF Heating in the LHC

Since June 2011 the rapid increase of the luminosity performance of the LHC has come at the expense of both increased temperature and pressure of specific, near-beam, LHC equipment. In some cases, this beam induced heating has caused delays while equipment cool-down, beam dumps and even degradation of some devices. This contribution gathers the observations of beam induced heating, attributed to longitudinal beam coupling impedance, their current level of understanding and possible actions planned to be implemented during the 1st LHC Long Shutdown (LS1) in 2013-2014

Experimental verification for a collimator with in-jaw beam position monitors

At present the beam based alignment of the LHC collimators is performed by touching the beam halo with the two jaws of each device. This method requires dedicated fills at low intensities that are done infrequently because the procedure is time consuming. This limits the operational flexibility in particular in the case of changes of optics and orbit configuration in the experimental regions. The system performance relies on the machine reproducibility and regular loss maps to validate the settings. To overcome these limitations and to allow a continuous monitoring of the beam position at the collimators, a design with in-jaw beam position monitors was proposed and successfully tested with a mock-up collimator in the CERN-SPS. Extensive beam experiments allowed to determine the achievable accuracy of the jaw alignment for single and multi-turn operation. In this paper the results of these experiments are discussed. The measured alignment accuracy is compared to the accuracies achieved with the present collimators in the LHC.peer-reviewe

Electromagnetic Simulations of an Embedded BPM in Collimator Jaws

Next gen­er­a­tion of the LHC col­li­ma­tors will be equipped with but­ton beam po­si­tion mon­i­tors (BPMs) em­bed­ded into the col­li­ma­tor jaws. Such a so­lu­tion will im­prove the ac­cu­ra­cy of the jaw align­ment with respect to the beam and re­duce the beam time nec­es­sary for the collima­tor setup. This paper de­scribes re­sults of elec­tro­mag­net­ic simu­la­tions of the jaw BPMs per­formed with the CST Par­ti­cle Stu­dio suite, aimed at char­ac­ter­i­sa­tion of the BPMs as well as the simulation soft­ware it­self. The re­sults are com­pared to the mea­sure­ments ob­tained with beam on a pro­to­type sys­tem in­stalled in the CERN SPS

Embedded Collimator Beam Position Monitors

The LHC col­li­ma­tion sys­tem is cru­cial for safe and re­li­able op­er­a­tion of pro­ton beams with 350 MJ stored en­er­gy. Cur­rent­ly the col­li­ma­tor set-up is per­formed by ob­serv­ing beam loss­es when ap­proach­ing the colli­ma­tor jaws to the beam. For all 100 LHC mov­able col­li­ma­tors the pro­ce­dure may take sev­er­al hours and since it has to be re­peat­ed whenev­er the beam con­fig­u­ra­tion changes sig­nif­i­cant­ly, the col­li­ma­tor setup has an im­por­tant im­pact on the over­all ma­chine op­er­a­tion efficien­cy. To re­duce the col­li­ma­tor setup time by two or­ders of magni­tude the next gen­er­a­tion of the LHC col­li­ma­tors will be equipped with but­ton beam po­si­tion mon­i­tors (BPMs) em­bed­ded into the collimator jaws. This paper de­scribes the BPM de­sign and pre­sents proto­type re­sults ob­tained with beam in the CERN-SPS

Beam position monitor R&D for keV ion beams

Beams of cooled antiprotons at keV energies shall be provided by the Ultra-low energy Storage Ring (USR) at the Facility for Low energy Antiproton and Ion Research (FLAIR) and the Extra Low ENergy Antiproton ring (ELENA) at CERN's Antiproton Decelerator (AD) facility. Both storage rings put challenging demands on the beam position monitoring (BPM) system as their capacitive pick-ups should be capable of determining the beam position of beams at low intensities and low velocities, close to the noise level of state-of-the-art electronics. In this contribution we describe the design and anticipated performance of BPMs for low-energy ion beams with a focus on the ELENA orbit measurement systems. We also present the particular challenges encountered in the numerical simulation of pickup response at very low beta values. Finally, we provide an outlook on how the implementation of faster algorithms for the simulation of BPM characteristics could potentially help speed up such studies considerably

EMBEDDED COLLIMATOR BEAM POSITION MONITORS

Abstract The LHC collimation system is crucial for safe and reliable operation of proton beams with 350 MJ stored energy. Currently the collimator set-up is performed by observing beam losses when approaching the collimator jaws to the beam. For about 100 LHC movable collimators the procedure may take several hours and since it has to be repeated whenever the beam configuration changes significantly, the collimator setup has an important impact on the overall machine operation efficiency. To reduce the collimator setup time by two orders of magnitude the next generation of the LHC collimators will be equipped with button beam position monitors (BPMs) embedded into the collimator jaws. This paper describes the BPM design and presents prototype results obtained with beam in the CERN-SPS