Study of hybrid photonic band gap resonators for particle accelerators

Masullo, M.R.; Andreone, A.; Gennaro, Emiliano Di; Albanese, Steve; Francomacaro, F.; Panniello, M.; Vaccaro, V. G.; Lamura, G.

doi:10.1002/mop.22016

Cited by 15 publications

(13 citation statements)

References 5 publications

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“…The use of superconducting plates could be also foreseen, along the lines of the results presented in Ref. 3. In this last case, however, a deeper study should be undertaken in order to understand to what extent the improvement in the cavity performance would justify the higher complexity introduced by the necessity of operating at 4 K (or even less).…”

Section: S/m)mentioning

confidence: 99%

Mode confinement in photonic quasicrystal point-defect cavities for particle accelerators

Gennaro

Savo

Andreone

et al. 2008

Applied Physics Letters

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In this Letter, we present a study of the confinement properties of point-defect resonators in finite-size photonic-bandgap structures composed of aperiodic arrangements of dielectric rods, with special emphasis on their use for the design of cavities for particle accelerators. Specifically, for representative geometries, we study the properties of the fundamental mode (as a function of the filling fraction, structure size, and losses) via 2-D and 3-D full-wave numerical simulations, as well as microwave measurements at room temperature. Results indicate that, for reduced-size structures, aperiodic geometries exhibit superior confinement properties by comparison with periodic ones.A promising approach to the development of new types of compact, efficient microwave particle accelerators is to realize structures having higher frequencies of operation, since this can increase the accelerating field gradient and reduce the power consumption 1 . Unfortunately, in a particle accelerator, the higher the frequency, the stronger the excitation (by the wakefield effect) of higher order modes (HOMs), with a significant reduction of the beam stability. Nowadays accelerators operate at frequencies < ∼ 1 GHz, and they usually rely on waveguide-based HOM dampers in order to efficiently suppress the wakefields. However, at higher ( > ∼ 10 GHz) working frequencies, the standard configurations used for HOM damping become rather cumbersome or even technically unfeasible.In the past, open metallic photonic-crystal (PC) cavities, based on periodic arrangements of inclusions, have been proposed as candidates for a new generation of accelerating cells since they exhibit electromagnetic (EM) responses that can be highly selective in frequency. This property (and others related) arises from the formation of photonic bandgaps (PBGs), whereby multiple scattering of waves by periodic lattices of inclusions acts to prevent the propagation of EM waves within certain frequency ranges. In these structures, an open resonator can be easily created by introducing a lattice defect, e.g., by removing one inclusion. Unlike conventional closed cavities, such a point-defect PBG cavity can be designed to support only one bound mode (strongly localized within the defect region), and mostly extended HOMs. This suggests the possibility of using PBG-based cavities for effective HOM wakefield suppression, without the need for mode couplers or detuning. Indeed, a prototype of a large-gradient accelerator that relies on a metallic PBG structure has been successfully fabricated and experimentally characterized 2 . Superconducting prototypes have been also tested at 4 K, showing quality factors up to ∼ 10 5 , limited by radiation losses only 3 . All-dielectric or hybrid-dielectric PBG structures could also be used, thereby eliminating or reducing the characteristic metallic losses at the frequency of operation, even if at the expense of an increased radiative contribution 4 .Moreover, it should be observed that spatial periodicity is not an essential ingredient...

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Section: S/m)mentioning

confidence: 99%

Mode confinement in photonic quasicrystal point-defect cavities for particle accelerators

Gennaro

Savo

Andreone

et al. 2008

Applied Physics Letters

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“…The experiment in Ref. [4] successfully secured the rods simply by endplate pressure. On the other hand, covering the region of conductor suffering the maximum magnetic field with dielectric could suppress the breakdown mechanism.…”

Section: Surface Fieldsmentioning

confidence: 99%

“…Photonic crystals (PhCs) have recently attracted interest from the accelerator community [1][2][3][4][5][6][7][8][9][10][11][12] for the following reasons: (1) PhCs enable the construction of accelerator cavities using dielectric materials. (2) PhC cavities intrinsically provide a wakefield damping mechanism.…”

Section: Introductionmentioning

confidence: 99%

Origin and reduction of wakefields in photonic crystal accelerator cavities

Bauer

Werner

Cary

2014

Phys. Rev. ST Accel. Beams

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Photonic crystal (PhC) defect cavities that support an accelerating mode tend to trap unwanted higherorder modes (HOMs) corresponding to zero-group-velocity PhC lattice modes at frequencies near the top of bandgaps. The effect is explained quite generally by photonic band and perturbation theoretical arguments. Transverse wakefields resulting from this effect are observed (via simulation) in a 12 GHz hybrid dielectric PhC accelerating cavity based on a triangular lattice of sapphire rods. These wakefields are, on average, an order of magnitude higher than those in the 12 GHz waveguide-damped Compact Linear Collider copper cavities. The avoidance of translational symmetry (and, thus, the bandgap concept) can dramatically improve HOM damping in PhC-based structures.

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“…Recent advances in the study of photonic structures for accelerator applications include research on hybrid structures consisting of metallic and dielectric components [10,11]; research on quasicrystals [12]; research on disordered photonic structures [13]; research on truncated, optimized photonic structures [14]; and theoretical research on wakefields [15].…”

Section: Introductionmentioning

confidence: 99%

X-band photonic band-gap accelerator structure breakdown experiment

Marsh

Shapiro

Temkin

et al. 2011

Phys. Rev. ST Accel. Beams

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In order to understand the performance of photonic band-gap (PBG) structures under realistic high gradient, high power, high repetition rate operation, a PBG accelerator structure was designed and tested at X band (11.424 GHz). The structure consisted of a single test cell with matching cells before and after the structure. The design followed principles previously established in testing a series of conventional pillbox structures. The PBG structure was tested at an accelerating gradient of 65 MV=m yielding a breakdown rate of two breakdowns per hour at 60 Hz. An accelerating gradient above 110 MV=m was demonstrated at a higher breakdown rate. Significant pulsed heating occurred on the surface of the inner rods of the PBG structure, with a temperature rise of 85 K estimated when operating in 100 ns pulses at a gradient of 100 MV=m and a surface magnetic field of 890 kA=m. A temperature rise of up to 250 K was estimated for some shots. The iris surfaces, the location of peak electric field, surprisingly had no damage, but the inner rods, the location of the peak magnetic fields and a large temperature rise, had significant damage. Breakdown in accelerator structures is generally understood in terms of electric field effects. These PBG structure results highlight the unexpected role of magnetic fields in breakdown. The hypothesis is presented that the moderate level electric field on the inner rods, about 14 MV=m, is enhanced at small tips and projections caused by pulsed heating, leading to breakdown. Future PBG structures should be built to minimize pulsed surface heating and temperature rise.

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Study of hybrid photonic band gap resonators for particle accelerators

Cited by 15 publications

References 5 publications

Mode confinement in photonic quasicrystal point-defect cavities for particle accelerators

Mode confinement in photonic quasicrystal point-defect cavities for particle accelerators

Origin and reduction of wakefields in photonic crystal accelerator cavities

X-band photonic band-gap accelerator structure breakdown experiment

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