Implications of beam filling patterns on the design of recirculating energy recovery linacs

Setiniyaz, Sadiq; Apsimon, R.; Williams, Peter H.

doi:10.1103/physrevaccelbeams.23.072002

Cited by 6 publications

(6 citation statements)

References 19 publications

(30 reference statements)

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“…As previously mentioned and also discussed in more detail in [33], SP schemes have the property that the sequence of bunch turn numbers in a packet does not change from one turn to the next. It can be shown that all filling patterns will have a unique recirculation scheme to form an SP scheme, but the converse is not necessarily true.…”

Section: A Worked Example: Sp Schemesmentioning

confidence: 89%

“…From [33] it is known that for any choice of bunch filling pattern and recirculation scheme, the filling pattern will repeat every N turns, or in some cases an integer divisor of N . Additionally, in [33] the concept of a sequence preserving (SP) scheme is discussed, whereby for a given filling pattern, a recirculation scheme can be chosen such that the sequence of bunch turn numbers in a packet is the same on each turn. For SP schemes, we see that the bunch packets are equivalent for all turns and so we can also trivially see that this will indeed be periodic over N turns.…”

Section: Analytical Modelmentioning

confidence: 99%

“…This becomes important when considering multi-pass ERLs which, having now been demonstrated experimentally [32], feature in many designs for future ERL facilities due to the obvious advantage of providing higher beam energies without concomitant increase in the number of accelerating structures. The effect of the filling pattern, which describes the order in which bunches are injected into the ERL over subsequent turns, has in a previous publication [33] been shown to have a major impact on the stability of the RF system. Just as the fundamental mode and RF power are affected differently by our choice of beam line topology and filling pattern, the threshold current of regenerative BBU is also dependent on these parameters.…”

Section: Introductionmentioning

confidence: 99%

“…Filling patterns are used to describe the order in which bunches are injected into a ring on subsequent turns, here we use the concept (introduced in [33]) of intra-packet blocks to describe the position they occupy on each turn. For example, for a 6-turn ERL (3 accelerating passes and 3 decelerating), the filling pattern [1 2 3 4 5 6] indicates that the first bunch goes to the first intra-packet block, the second bunch goes to the second block, and so on.…”

Section: Introductionmentioning

confidence: 99%

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Filling Pattern Dependence of Regenerative Beam Breakup Instability in Energy Recovery Linacs

Setiniyaz,

Apsimon,

Williams

2021

Preprint

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Beam breakup instability is a potential issue for all particle accelerators and is often the limiting factor for the maximum beam current that can be achieved. This is particularly relevant for Energy Recovery Linacs with multiple passes where a relatively small amount of charge can result in a large beam current. Recent studies have shown that the choice of filling pattern and recirculation scheme for a multi-pass energy recovery linac can drastically affect the interactions between the beam and RF system. In this paper we further explore this topic to study how filling patterns affect the beam breakup instability and how this can allow us to optimise the design in order to minimise this effect. We present a theoretical model of the beam-RF interaction as well as numerical modeling and show that the threshold current can vary by factors of 2-4, and potentially even more depending on the machine design parameters. Therefore a judicious choice of filling pattern can greatly increase the onset of BBU, expanding the utility of future ERLs.

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Section: A Worked Example: Sp Schemesmentioning

confidence: 89%

Section: Analytical Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Filling Pattern Dependence of Regenerative Beam Breakup Instability in Energy Recovery Linacs

Setiniyaz,

Apsimon,

Williams

2021

Preprint

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“…As such this methodology establishes the single bunch longitudinal dynamics in steady state. The consequences of relaxing the first two conditions are explored in [5,6], where we see that the ordering of bunches, or filling pattern, affects LLRF stability and the regenerative BBU threshold. Transient effects will be explored in a subsequent paper.…”

Section: Definitions and Assumptionsmentioning

confidence: 99%

Construction of Self-Consistent Longitudinal Matches in Multi-Pass Energy Recovery Linacs

Segurana,

Bailey,

Williams

2021

Preprint

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Any proposal for an accelerator facility based upon a multipass Energy Recovery Linac (ERL) must possess a self-consistent match in longitudinal phase space, not just transverse phase space. We therefore present a semi-analytic method to determine self-consistent longitudinal matches in any multipass ERL. We apply this method in collider scenarios (embodying an energy spread minimising match) and FEL scenarios (embodying a compressive match), and discuss the consequences of each. As an example of the utility of the method, we prove that the choice of common or separate recirculation transport determines the feasibility of longitudinal matches in cases where disruption, such as synchrotron radiation loss, exists. We show that any high energy multipass ERL collider based upon common recirculation transport will require special care to produce a self-consistent longitudinal match, but that one based upon separate transport is readily available. Furthermore we show that any high energy multipass ERL FEL driver based upon common recirculation transport requires a larger resultant rf beam load than the one based on separate transport, favouring the separate transport designs.

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The Large Hadron–Electron Collider at the HL-LHC

Agostini

Aksakal

Alekhin

et al. 2021

J. Phys. G: Nucl. Part. Phys.

128

129

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The Large Hadron–Electron Collider (LHeC) is designed to move the field of deep inelastic scattering (DIS) to the energy and intensity frontier of particle physics. Exploiting energy-recovery technology, it collides a novel, intense electron beam with a proton or ion beam from the High-Luminosity Large Hadron Collider (HL-LHC). The accelerator and interaction region are designed for concurrent electron–proton and proton–proton operations. This report represents an update to the LHeC’s conceptual design report (CDR), published in 2012. It comprises new results on the parton structure of the proton and heavier nuclei, QCD dynamics, and electroweak and top-quark physics. It is shown how the LHeC will open a new chapter of nuclear particle physics by extending the accessible kinematic range of lepton–nucleus scattering by several orders of magnitude. Due to its enhanced luminosity and large energy and the cleanliness of the final hadronic states, the LHeC has a strong Higgs physics programme and its own discovery potential for new physics. Building on the 2012 CDR, this report contains a detailed updated design for the energy-recovery electron linac (ERL), including a new lattice, magnet and superconducting radio-frequency technology, and further components. Challenges of energy recovery are described, and the lower-energy, high-current, three-turn ERL facility, PERLE at Orsay, is presented, which uses the LHeC characteristics serving as a development facility for the design and operation of the LHeC. An updated detector design is presented corresponding to the acceptance, resolution, and calibration goals that arise from the Higgs and parton-density-function physics programmes. This paper also presents novel results for the Future Circular Collider in electron–hadron (FCC-eh) mode, which utilises the same ERL technology to further extend the reach of DIS to even higher centre-of-mass energies.

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Implications of beam filling patterns on the design of recirculating energy recovery linacs

Cited by 6 publications

References 19 publications

Filling Pattern Dependence of Regenerative Beam Breakup Instability in Energy Recovery Linacs

Filling Pattern Dependence of Regenerative Beam Breakup Instability in Energy Recovery Linacs

Construction of Self-Consistent Longitudinal Matches in Multi-Pass Energy Recovery Linacs

The Large Hadron–Electron Collider at the HL-LHC

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