Design and Manufacture of Tunable Permanent Magnet Based Quadrupole for Next Generation Electron-Ion Colliders [Slides]

Choi, Hyemi; Jasinski, Melania; Haley, Lori; Patches, Daniel

doi:10.2172/1509895

Cited by 3 publications

(8 citation statements)

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“…In all, 12 Halbach cylinders were used in experiments described in this paper. This work and other tests in our laboratory using nominal proton energies of 127, 157, and 186 MeV (range in water of 98.3, 151.1, and 197.81 mm, respectively) have shown that the magnets are capable of producing beam spots of high symmetry, indicating that the high-field magnets can be manufactured with sufficient quality for use in radiosurgery (McAuley et al 2015a, Choi et al 2016. The permanent magnet assemblies require no electric power or control circuitry, and no cryogenic cooling.…”

Section: Discussionmentioning

confidence: 70%

“…Magnets were manufactured as triplet sets with the same gradient and diameter. However, in each triplet two magnets had cylinder lengths of 40 mm while the length of the third was 68 mm-a ratio of 1.7 (Choi et al 2016). To first order, for equal lens power in each plane, this ratio can be shown to be strictly less than 2 with maximum power when the ratio is 1.6.…”

Section: Quadrupole Halbach Cylindersmentioning

confidence: 99%

“…The Halbach cylinders used in the present research have been described previously (McAuley et al 2015a, Choi et al 2016. In the present study we used 12 quadrupole focusing magnets manufactured by a commercial vendor (Electron Energy Corporation, Landisville, PA) to our specifications, including field gradient, bore diameter and magnet length.…”

Section: Quadrupole Halbach Cylindersmentioning

confidence: 99%

“…The magnetic cylinders had nominal gradients of 100, 150, 200 and 250 T m −1 . Magnets with the former two gradients had cylinder diameters of 20 mm, whereas the latter two had diameters of 10 mm (McAuley et al 2015a, Choi 2016). Magnets were manufactured as triplet sets with the same gradient and diameter.…”

Section: Quadrupole Halbach Cylindersmentioning

confidence: 99%

“…In addition, peak-to-entrance and efficiency performance tended to increase with larger magnet gradients and larger initial diameter focused beams (McAuley et al 2018). The focusing magnets were modeled with the nominal specifications of actual magnets that were commercially manufactured for our laboratory as Halbach cylinders (Halbach 1980, McAuley et al 2015a, Choi et al 2016.…”

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confidence: 99%

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Experimental validation of magnetically focused proton beams for radiosurgery

et al. 2019

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Earlier detection of cancerous lesions due to improved imaging technology and patient screening is fueling a trend in radiation medicine to irradiate increasingly smaller targets. Proton radiosurgery has advantages compared to other external-beam radiation modalities when treating small lesions, including the delivery of high doses to target volumes with three to four treatment beams. However, for small-diameter beams (<1.0 cm), beam broadening due multiple Coulomb scattering (MCS) leads to degradation of the Bragg peak that manifests itself as lower peak-to-entrance dose (P/E) ratios and reduced rates of dose delivery to the radiation target. The effects of beam degradation are typically ameliorated by employing additional treatment beams, but this leads to increased integral dose and even longer treatment times that work against the advantages of proton radiosurgery. Magnetic focusing immediately upstream from the patient could help compensate for the effects of MCS, potentially leading to radiosurgical treatments with lower entrance doses, fewer beams, reduced integral doses, improved therapeutic ratios, and decreased treatment times (McAuley et al 2013(McAuley et al , 2015a(McAuley et al , 2018.

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Section: Discussionmentioning

confidence: 70%

Section: Quadrupole Halbach Cylindersmentioning

confidence: 99%

Section: Quadrupole Halbach Cylindersmentioning

confidence: 99%

Section: Quadrupole Halbach Cylindersmentioning

confidence: 99%

mentioning

confidence: 99%

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Experimental validation of magnetically focused proton beams for radiosurgery

et al. 2019

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Monte Carlo evaluation of magnetically focused proton beams for radiosurgery

et al. 2018

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The purpose of this project is to investigate the advantages in dose distribution and delivery of proton beams focused by a triplet of quadrupole magnets in the context of potential radiosurgery treatments. Monte Carlo simulations were performed using various configurations of three quadrupole magnets located immediately upstream of a water phantom. Magnet parameters were selected to match what can be commercially manufactured as assemblies of rare-earth permanent magnetic materials. Focused unmodulated proton beams with a range of ~10 cm in water were target matched with passive collimated beams (the current beam delivery method for proton radiosurgery) and properties of transverse dose, depth dose and volumetric dose distributions were compared. Magnetically focused beams delivered beam spots of low eccentricity to Bragg peak depth with full widths at the 90% reference dose contour from ~2.5 to 5 mm. When focused initial beam diameters were larger than matching unfocused beams (10 of 11 cases) the focused beams showed 16%-83% larger peak-to-entrance dose ratios and 1.3 to 3.4-fold increases in dose delivery efficiency. Peak-to-entrance and efficiency benefits tended to increase with larger magnet gradients and larger initial diameter focused beams. Finally, it was observed that focusing tended to shift dose in the water phantom volume from the 80%-20% dose range to below 20% of reference dose, compared to unfocused beams. We conclude that focusing proton beams immediately upstream from tissue entry using permanent magnet assemblies can produce beams with larger peak-to-entrance dose ratios and increased dose delivery efficiencies. Such beams could potentially be used in the clinic to irradiate small-field radiosurgical targets with fewer beams, lower entrance dose and shorter treatment times.

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Monte Carlo evaluation of high-gradient magnetically focused planar proton minibeams in a passive nozzle

McAuley¹,

Teran²,

Slater³

et al. 2022

Phys. Med. Biol.

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Objective To investigate the potential of using a single quadrupole magnet with a high magnetic field gradient to create planar minibeams suitable for clinical applications of proton minibeam radiation therapy Approach We performed Monte Carlo simulations involving single quadrupole Halbach cylinders in a passively scattered nozzle in clinical use for proton therapy. Pencil beams produced by the nozzle of 10 to 15 mm initial diameters and particle range of ~ 10 to 20 cm in water were focused by magnets with field gradients of 225 to 350 T/m and cylinder lengths of 80 to 110 mm to produce very narrow elongated (planar) beamlets. The corresponding dose distributions were scored in a water phantom. Composite minibeam dose distributions composed from three beamlets were created by laterally shifting copies of the single beamlet distribution to either side of a central beamlet. Modulated beamlets (with 18 to 30 mm nominal central SOBP) and corresponding composites dose distributions were created in a similar manner. Collimated minibeams were also compared with beams focused using one magnet/particle range combination. Main Results The focusing magnets produced planar beamlets with minimum lateral FWHM of ~1.1 - 1.6 mm. Dose distributions composed from three unmodulated beamlets showed a high degree of proximal spatial fractionation and a homogeneous target dose. Maximal peak-to-valley dose ratios (PVDR) for the unmodulated beams ranged from 32 to 324, and composite modulated beam showed maximal PVDR ranging from 32 to 102 and SOBPs with good target dose coverage. Significance Advantages of the high-gradient magnets include the ability to focus beams with phase space parameters that reflect beams in operation today, and post-waist particle divergence allowing larger beamlet separations and thus larger PVDR. Our results suggest that high gradient quadrupole magnets could be useful to focus beams of moderate emittance in clinical proton therapy.

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Design and Manufacture of Tunable Permanent Magnet Based Quadrupole for Next Generation Electron-Ion Colliders [Slides]

Cited by 3 publications

References 0 publications

Experimental validation of magnetically focused proton beams for radiosurgery

Experimental validation of magnetically focused proton beams for radiosurgery

Monte Carlo evaluation of magnetically focused proton beams for radiosurgery

Monte Carlo evaluation of high-gradient magnetically focused planar proton minibeams in a passive nozzle

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