Ionisation Cooling Lattices for the Neutrino Factory

The future accelerator complex of the Neutrino Factory will have an excellent precision and outstanding discovery reach, and is therefore a facility of choice for precise neutrino oscillation measurements. In the Neutrino Factory, muons are accumulated into storage rings and decay to neutrinos. However, due to the fact that the muon beam is produced occupying a large transverse phase-space, it is essential that its emittance is decreased using ionisation cooling. The reference ionisation cooling lattice of the Neutrino Factory has a large magnetic field at the position of the RF cavities, and there is a strong concern this can lead to RF breakdown. Therefore, there lies a great necessity for alternative cooling lattices to be found. This thesis presents several cooling lattices that were designed aiming to mitigate the problem of the RF breakdown in the presence of a magnetic field, that the reference lattice suffers from. In particular, amongst these lattices, a promising new configuration which makes use of a pair of opposite polarity and homocentric coils, named “Bucked Coils”, is presented. The Bucked Coils lattice not only manages to successfully achieve a virtually zero longitudinal magnetic field at the position of the RF cavities, but also obtains a better transmission than the reference lattice. A detailed comparison between the reference and the new lattices is presented with respect to the magnetic field, transmission and cooling efficiency. A possible extension of the work is also discussed. A six-dimensional cooling could be used at a Neutrino Factory but is essential for a Muon Collider. Another novel configuration, which aims to achieve 6D ionisation cooling, is presented in this thesis. This new lattice creates dispersion with the use of dipoles, and a correlation between energy loss and position with the use of wedge absorbers. A detailed description of this lattice configuration and analysis is given, together with preliminary results

Prediction of Beam Losses during Crab Cavity Quenches at the HL-LHC

Studies of the crab cavities at KEKB revealed that the RF phase could shift by up to 50o within ~50 us during a quench; while the cavity voltage is still at approximately 75% of its nominal amplitude. If such a failure were to occur on the HL-LHC crab cavities, it is likely that the machine would sustain substantial damage to the beam line and surrounding infrastructure due to uncontrolled beam loss before the machine protection system could dump the beam. We have developed a low-level RF system model, including detuning mechanisms and beam loading, and use this to simulate the behaviour of a crab cavity during a quench, modeling the low-level RF system, detuning mechanisms and beam loading. We supplement this with measurement data of the actual RF response of the proof of principle Double-Quarter Wave Crab Cravity during a quench. Extrapolating these measurements to the HL-LHC, we show that Lorentz Force detuning is the dominant effect leading to phase shifts in the crab cavity during quenches; rather than pressure detuning which is expected to be dominant for the KEKB crab cavities. The total frequency shift for the HL-LHC crab cavities during quenches is expected to be about 460 Hz, leading to a phase shift of no more than 3o. The results of the quench model are read into a particle tracking simulation, SixTrack, and used to determine the effect of quenches on the HL-LHC beam. The quench model has been benchmarked against the KEKB experimental measurements. In this paper we present the results of the simulations on a crab cavity failure for HL-LHC as well as for the SPS and show that beam loss is negligible when using a realistic low-level RF response.Comment: 21 Pages, 22 figures, Submitted to PRA

CERN Alumni Third Collisions

Link: https://alumni.cern/news/1804220 Topics explored: • How can I apply the growth mindset to the career application process and my career planning? • In what ways can I identify my key transferable skills and competences? • How can I navigate a career pivot? What if I am climbing the ladder and discover the ladder is leaning on the wrong wall? • What does self-value look like for high achievers? • How can I make career decisions that factor in holistic living and quality of life? • What is the value of career stories? (And why are career stories more powerful than advice?) • Why should I embrace uncertainty, curiosity and stepping out of my comfort zone

Design of a Fast Single-turn Extraction for the ESSnuSB Accumulator

In the European Spallation Source (ESS) neutrino Super Beam (ESSnuSB), a very intense neutrino beam will be produced in order to measure with a high precision the CP violating angle at the 2nd oscillation maximum. An accumulator ring is included in the ESSnuSB design that allows converting a series of linac pulses to single intense pulses that subsequently will bombard the neutrino production targets. This report presents the optics system for a one-turn fast extraction ejecting the proton beam from the ESSnuSB accumulator ring into the extraction septum gap and further deflecting it into the ring-to-target beam transport line

Beam-based measurement of the skew-sextupolar component of the radio frequency field of a HL-LHC-type crab-cavity

Two High Luminosity Large Hadron Collider (LHC) type crab-cavities have been installed in the CERN SPS for testing purposes. An attempt to characterize the skew-sextupolar component of the radio frequency field of the crab-cavity ($a_3$) has been carried out by means of beam-based techniques using turn-by-turn monitoring of the betatron motion. The skew nature of $a_3$ couples the horizontal and vertical betatron motions through a non-linear term. Therefore by exciting the horizontal betatron motion it was possible to observe a spectral line in the vertical beam motion driven by the non-linear coupling at the characteristic frequency $2Q_x$. A measurement of the magnitude of $a_3$ was thus obtained by characterizing amplitude and phase of such line. The results of the measurements are discussed here

Numerical tools for Crab Cavity simulations

This note gives the steps to be followed in order to include the crab cavities module in MAD-X for tracking simulations in SixTrack. Examples of checks that aim to verify that the system is implemented as expected are provided; these checks are important to be done before launching large simulations using, for example, SixDesk

Beam dynamics simulations with Crab Cavities in the SPS machine

The LHC Upgrade, called High Luminosity LHC, aims to increase the integrated luminosity by a factor of 10. To achieve this, the project relies on a number of key innovative technologies, including the use of superconducting Crab Cavities with ultra-precise phase control for beam rotation. A set of prototype Crab Cavities has been recently installed in the second largest machine of CERN, the Super Proton Synchrotron (SPS), that operated as a test-bed from May to November of 2018. The tight LHC constraints call for axially non-symmetric cavity designs that introduce high order multipole components. Furthermore, the Crab Cavities in the presence of SPS non-linearities can affect the long term stability of the beam. This paper presents how the SPS dynamic aperture is affected for different cavity, machine and beam configurations

Beam-based measurements of the skew-sextupolar component of the radio frequency field of a HL-LHC-type crab-cavity

Two High Luminosity Large Hadron Collider (LHC) crab-cavity types have been installed in 2018 in the CERN SPS for testing purposes. An attempt to characterize the skew-sextupolar component (a3) of the radio frequency field of the crab-cavity through beam-based techniques has been carried out. By monitoring with turn-by-turn beam position monitors the betatron motion, it was possible to study the non-linear coupling between the transverse planes resulting from the skew nature of the a3 component of the crab-cavity. A measurement of the magnitude of a3 was thus obtained by characterizing amplitude and phase of some of the spectral lines induced by such non-linear coupling. Particular attention was required to disentangle the a3 contribution of the crab-cavity from the SPS optics non-linearities, that unexpectedly was found to play a dominant role over the faint signal induced by the crab-cavity skew-sextupolar component. A detailed description of the measurements, analysis and the results are here presented

SPS Long Term Stability Studies in the Presence of Crab Cavities and High Order Multipoles

A local Crab Cavity (CC) scheme will recover the head-on collisions at the IP of the High Luminosity LHC (HL-LHC), which aims to increase the LHC luminosity by a factor of 3-10. The tight space constraints at the CC location result in axially non-symmetric cavity designs that introduce high order multipole CC components. The impact of these high order components on the long term stability of the beam in the SPS machine, where two prototype crab cavities are presently installed in the CERN SPS to perform tests with beam, is presented. Furthermore, the Dynamic Aperture is studied in the presence of the SPS errors. Future plans are discussed

Conceptual design and modeling of particle-matter interaction cooling systems for muon based applications

An ionization cooling channel is a tightly spaced lattice containing absorbers for reducing the momentum of the muon beam, rf cavities for restoring the longitudinal momentum, and strong solenoids for focusing. Such a lattice can be an essential feature for fundamental high-energy physics applications. In this paper we design, simulate, and compare four individual cooling schemes that rely on ionization cooling. We establish a scaling characterizing the impact of rf gradient limitations on the overall performance and systematically compare important lattice parameters such as the required magnetic fields and the number of cavities and absorber lengths for each cooling scenario. We discuss approaches for reducing the peak magnetic field inside the rf cavities by either increasing the lattice cell length or adopting a novel bucked-coil configuration. We numerically examine the performance of our proposed channels with two independent codes that fully incorporate all basic particle-matter-interaction physical processes