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Bruno Muratori

Daresbury Laboratory, Accelerator Science and Technology Centre (ASTeC), Faculty Member

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Phone: 0044 (0) 1925 603281
Address: Cockcroft Institute and Daresbury Laboratory
Keckwick lane
Warrington WA4 4AD
Cheshire
UK

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Papers by Bruno Muratori

A Laser Heater for CLARA

CLARA is a new FEL test facility, being developed at STFC Daresbury Laboratory in UK, based on a ... more CLARA is a new FEL test facility, being developed at STFC Daresbury Laboratory in UK, based on a high brightness electron linac. The electron beam of CLARA can potentially be affected by the longitudinal microbunching instability leading to a degradation of the beam quality. The inclusion of a laser heater in the linac design can allow control of the microbunching instability, the study of microbunching and deliberate increase of the final energy spread to study energy spread requirements of the FEL schemes tested at CLARA. We present the initial design and layout of the laser heater system for CLARA and its expected performance.

Concept of luminosity

The performance of particle colliders is usually quantified by the beam energy and the luminosity... more The performance of particle colliders is usually quantified by the beam energy and the luminosity. We derive the expressions for the luminosity in case of bunched beams in terms of the beam parameters and the geometry. The implications of additional features such as crossing angle, offsets and hourglass effect on the luminosity are calculated. Important operational aspects like integrated luminosity, space and time structure of interactions etc. are discussed. The measurement of luminosity for e + e − as well as hadron colliders and the methods for the calibration of the absolute luminosity are described.

Project-Based Cooperative Learning in Accelerator Science and Technology Education

8th Int. Particle Accelerator Conf. (IPAC'17), Copenhagen, Denmark, 14â19 May, 2017, Jun 1, 2017

Project-based learning uses a project to enable students to learn practical knowledge, often supp... more Project-based learning uses a project to enable students to learn practical knowledge, often supplemented with some introductory lectures. (PrBL) has been employed at the Cockcroft Institute as part of their postgraduate programme in particle accelerator physics and engineering. 40 students have taken part in two schools. The students are made to work in groups to enable cooperative learning to further enhance learning. The outcome for these students is compared to a similar number of students taking conventional lecture based education and is shown to enhance the ability to apply knowledge.

Tracking Through Analytic Quadrupole Fringe Fields With GPT

6th Int. Particle Accelerator Conf. (IPAC'15), Richmond, VA, USA, May 3-8, 2015, Jun 1, 2015

In the early design stages it is customary to work with a highly simplified analytic model to des... more In the early design stages it is customary to work with a highly simplified analytic model to describe a beamline. Dipoles and quadrupoles are often based on hard-edged approximations. This is not only unrealistic, it also significantly slows down time-domain spacecharge tracking codes such as the General Particle Tracer (GPT) code. The underlying reason for the poor performance is that, despite the fact that the simple hard-edged field equations are fast to evaluate, they force the integration process to use excessively small step sizes near the field discontinuities in order to achieve the desired accuracy. In other words, the apparently simple equations turn out to be the most difficult ones to evaluate numerically. An obvious solution is to switch to field-maps, but this is not practical in the early design stages. In this contribution we show a new solution implemented in the GPT code based on analytical expressions for the fringes where the transverse size of the magnet is properly taken into account. In addition to producing more realistic results, the smooth fields increase tracking speed by over an order of magnitude for typical cases.

Characterisation of Electron Bunches from ALICE (ERLP) DC Photoinjector Gun at Two Different Laser Pulse Lengths

Presented at, Jun 23, 2008

In high-voltage DC photoinjector guns, the drive laser pulse duration affects the electron bunch ... more In high-voltage DC photoinjector guns, the drive laser pulse duration affects the electron bunch characteristics and is therefore an important subject for experimental investigation in order to optimise performance of the gun. Initial experimental studies into this effect have been carried out on ALICE (formerly the Energy Recovery Linac Prototype) photoinjector. During the commissioning of its DC photoinjector gun, electron bunch parameters were measured at two laser pulse durations, ~7 ps and ~28 ps FWHM. The shorter laser pulse is the intrinsic output pulse length of the laser, while the longer pulse was synthesised using a pulse stacker. The electron bunch parameters that were measured included transverse emittance, correlated and tilt compensated energy spectra and bunch length. The experimental results and their comparison with computer simulations are presented and discussed.

A Phase Space Tomography Diagnostic for Pitz

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Jun 26, 2006

The Photo Injector Test Facility at DESY in Zeuthen (PITZ) is a European collaboration developing... more The Photo Injector Test Facility at DESY in Zeuthen (PITZ) is a European collaboration developing RF photocathode electron guns for light source and linear collider projects. As part of the collaborative work being partially funded by the EU's FP6 programme ('EuroFEL', contract number 011935), CCLRC Daresbury Laboratory and DESY are designing and building a phase space tomography diagnostic based on a set of quadrupoles and view screens. In order to measure the beam emittance, four screens with intermediate quadrupole doublets will be used. The equipment will be installed and tested at PITZ as part of the facility upgrade presently ongoing. Following simulations of the gun using the ASTRA code at a range of energies, simulations of the electron beam parameters through the matching and tomography sections must be undertaken in order to specify the optimum arrangement of magnets and screens.

Multipole Fringe Fields

Presented at, 2011

When creating an initial model of an accelerator, one usually has to resort to a hard edge model ... more When creating an initial model of an accelerator, one usually has to resort to a hard edge model for the quadrupoles and higher order multipoles at the start of the project. Ordinarily, it is not until much later on that one has a field map for the given multipoles. This can be rather inconvenient when one is dealing with particularly thin elements or elements which are rather close together in a beamline as the hard edge model may be inadequate for the level of precision desired. For example, in the EMMA project, the two types of quadrupoles used are so close together that they are usually described by a single field map or via hard edge models. The first method has the desired accuracy but was not available at the start of the project and the second is known to be a rough approximation. In this paper, an analytic expression is derived and presented for fringe fields for a multipole of any order with a view to applying it to cases like EMMA.

Design and Principles of Synchrotrons and Circular Colliders

Springer eBooks, 2020

Lattice design in the context we will describe it here is the design and optimization of the prin... more Lattice design in the context we will describe it here is the design and optimization of the principle elements-the lattice cells-of a circular accelerator, and it includes the dedicated variation of the accelerator elements (as for example position and strength of the magnets in the machine) to obtain well defined and predictable parameters of the stored particle beam. It is therefore closely related to the theory of linear beam optics that has been described in Chap. 2 [1].

Comparison of Model vs. Reality for VELA

7th Int. Particle Accelerator Conf. (IPAC'16), Busan, Korea, May 8-13, 2016, Jun 1, 2016

The Lanczos potential for vacuum space–times with an Ernst potential

Journal of Mathematical Physics, Oct 1, 1998

By a particular choice of tetrad and coordinate systems, we find the Lanczos potential for genera... more By a particular choice of tetrad and coordinate systems, we find the Lanczos potential for general vacuum stationary axisymmetric space–times and for general vacuum cylindrically symmetric solutions. This result is particularly elegant and unifies the treatment of the Lanczos potential and the Ernst potential for vacuum stationary axially symmetric and cylindrically symmetric space–times. The Lanczos potential for such large classes of vacuum space–times is expressed very simply in terms of spin-coefficients for a null tetrad.

Luminosity and luminous region calculations for the LHC

The Luminosity and luminous region for an accelerator for bunched beams and a crossing angle are ... more The Luminosity and luminous region for an accelerator for bunched beams and a crossing angle are considered. Time averaged values for both are calculated based on the assumptions that the bunch length increases linearly and the intensity decreases exponentially. Specific calculations are made for the forthcoming Large Hadron Collider (LHC).

Luminosity levelling techniques for the LHC

arXiv (Cornell University), Oct 21, 2014

We present the possibilities for doing luminosity levelling at the LHC. We explore the merits and... more We present the possibilities for doing luminosity levelling at the LHC. We explore the merits and drawbacks of each option and briefly discuss the operational implications. The simplest option is levelling with an offset between the two beams. Crab cavities may also be used for levelling, as may a squeezing of the beam. There is also the possibility of using the crossing angle in order to do luminosity levelling. All of these options are explored, for the LHC and other possible new projects, together with their benefits and drawbacks.

Strong-Strong Simulations of β$^∗$-Levelling for Flat and Round Beams

Simulations of β * luminosity levelling using the strongstrong beam-beam code COMBI are undertake... more Simulations of β * luminosity levelling using the strongstrong beam-beam code COMBI are undertaken. Simulations for both flat and round beam profiles are discussed and analysed with respect to the coherent spectra. It is shown that bunches with a round beam profile will have a beambeam parameter that is independent of β * over the levelling steps. Flat bunches however will have a beam-beam parameter that is dependent on β * over the levelling steps since the beam aspect ratio will change. This will change the tune of the π-mode as the β * is levelled, which could lead to a resonance crossing.

Virtual VELA-CLARA: The Development of a Virtual Accelerator

9th Int. Particle Accelerator Conf. (IPAC'18), Vancouver, BC, Canada, April 29-May 4, 2018, Dec 21, 2018

A Virtual Accelerator (VA) has been developed to mimic the accelerators Versatile Electron Linear... more A Virtual Accelerator (VA) has been developed to mimic the accelerators Versatile Electron Linear Accelerator (VELA) and Compact Linear Accelerator for Research and Applications (CLARA). Its purpose is to test control room applications, run start-to-end simulations with multiple simulation codes, accurately reproduce measured beam properties, conduct 'virtual experiments'and gain insight into 'hidden beam parameters'. This paper gives an overview into the current progress in constructing this VA, detailing the areas of: developing a 'Virtual EPICS'control system, using multiple simulation codes (both particle tracking and analytic), the development of a 'Master Lattice'and the construction of a Python interface in which to run the VA.

New Injector for the Emma NS-Ffag Ring

EMMA is the world s first non-scaling FFAG which has recently demonstrated acceleration in the se... more EMMA is the world s first non-scaling FFAG which has recently demonstrated acceleration in the serpentine channel. At present, the electron beam is injected into EMMA from the ALICE accelerator. However, funding will be redirected to an Electron Beam Test Facility (EBTF) in the near future, therefore, in order to continue the broad portfolio of planned experiments required to characterize nonscaling FFAGs, it essential to consider an alternative injector. The paper looks at some possible alternatives and how the required beam for injection into EMMA can be achieved.

Phase Space Tomography Research at Daresbury

Matching with Space Charge

This paper explores the possibility of performing matching in the presence of space charge to an ... more This paper explores the possibility of performing matching in the presence of space charge to an acceptable and useful level. Space charge gives rise to a mismatch for beams at low energies. This mismatch can be very harmful for certain applications, for example the tomography diagnostic of the PITZ2 test line. In this case, the Twiss parameters at the start of the tomography section have to be as close as possible to the design ones. As can be shown by a thin lens approximation, all the Twiss parameters at the start of the tomography section are fully determined, as is the quadrupole strength, once the length of the FODO cells is chosen. With the presence of space charge it is necessary to introduce a modification to the original matching, itself performed with a standard optimizing routine. The idea is that this modification can only compensate for the linear part of space charge and it does so by changing the quadrupole strengths. The theory is verified by using an very simple test line consisting of just two quadrupoles and modeling it using GPT (General Particle Tracer). This results in modified values for the quadrupole strengths to accommodate the effect of space charge.

Gravitational Potentials and the Existence of Gravitational Green's Tensors

Modern Physics Letters A, Sep 21, 1998

The non-local part of the gravitational field Cabcd can be generated by the 16-component Lanczos ... more The non-local part of the gravitational field Cabcd can be generated by the 16-component Lanczos tensor potential Labc. When six gauge conditions are imposed, Labe;e=0, its ten degrees of freedom match those of the Weyl tensor. The Penrose wave equation for Cabcd can be independently derived from that for Labc. The consistency between Labc and Cabcd is also shown by the compatibility of their algebraic classifications. An unexpected insight into the relationship of Labc and Cabcd is found in &amp;amp;quot;Euclidean gravity&amp;amp;quot; which in turn leads to the introduction of a gravitational Green&amp;amp;#39;s tensor [Formula: see text] corresponding to the potential Labc.

Strong-Strong Simulations of Beta star Levelling for Flat and Round Beams

The HL-LHC project aims to reach larger peak luminosities, however this can lead to a high pile u... more The HL-LHC project aims to reach larger peak luminosities, however this can lead to a high pile up in the detectors. To control the pile up, luminosity levelling has been suggested. One proposed method is β*-luminosity levelling, in which beams collide at a larger than nominal β*. The β* is then reduced in steps as the beam intensity decays. This allows the luminosity to be kept constant over part of a physics fill. The use of round or flat optics will change the beam-beam effect of the head on collisions as well as the long range interactions. Here simulations of β* levelling are presented for the case of flat and round beam optics and the difference in terms of the beam-beam effect is highlighted.

Machine Layout and Performance

arXiv: Accelerator Physics, 2016

Chapter 2 in High-Luminosity Large Hadron Collider (HL-LHC) : Preliminary Design Report. The Larg... more Chapter 2 in High-Luminosity Large Hadron Collider (HL-LHC) : Preliminary Design Report. The Large Hadron Collider (LHC) is one of the largest scientific instruments ever built. Since opening up a new energy frontier for exploration in 2010, it has gathered a global user community of about 7,000 scientists working in fundamental particle physics and the physics of hadronic matter at extreme temperature and density. To sustain and extend its discovery potential, the LHC will need a major upgrade in the 2020s. This will increase its luminosity (rate of collisions) by a factor of five beyond the original design value and the integrated luminosity (total collisions created) by a factor ten. The LHC is already a highly complex and exquisitely optimised machine so this upgrade must be carefully conceived and will require about ten years to implement. The new configuration, known as High Luminosity LHC (HL-LHC), will rely on a number of key innovations that push accelerator technology beyo...