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Publications (10)2.28 Total impact

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    ABSTRACT: The main superconducting radio frequency (SRF) linacs of the international linear collider (ILC) operate at a frequency of 1.3GHz with a π phase advance per cell in the standing wave mode. An option being considered to reduce the overall footprint and project cost is to enhance the cavity gradient. The present baseline design for the main linacs of ILC demands the cavities to be able to reach a gradient of 35MV/m—although during commissioning and operation the gradient will be 31.5MV/m. This research concerns itself with the new cavity design with a view to reaching higher gradients. This design is focussed on minimising the surface electromagnetic fields and maximising the bandwidth of the accelerating mode. This new shape, which is referred to as the New Low Surface Field (NLSF) design. A design of a complete nine-cell cavity, including power couplers and higher order mode damping couplers is presented.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2014; · 1.14 Impact Factor
  • I. Nesmiyan, R. M. Jones, N. Juntong
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    ABSTRACT: This article focusses on a beam dynamics study for the linacs of the ILC. In particular, the impact of long-range transverse wakefields on the beam quality is studied for the case in which the ILC would be built using the new low surface field (NLSF) superconducting cavities. This presents an alternative design to the baseline TESLA-style cavities. The progress of the beam down ~10 km of each linac is simulated using the tracking computer code PLACET. In addition, the results of an analytical matrix method, in which the beam is subjected to identical wakefields from each cavity, are also presented. Both systematic and random errors, arising as a natural process during fabrication, are implemented in the beam tracking study. The latter source of error is found to be beneficial, as emittance dilution is reduced due to the beam receiving non-coherent kicks.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2014; · 1.14 Impact Factor
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    Ian Reginald Roy Shinton, Nawin Juntong
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    ABSTRACT: The resonant modes in the 9cell 3.9GHz bunch shaping cavity designed by FERMILAB in collaboration with DESY [1] and installed in FLASH at DESY were calculated up to the range of 10GHz in terms of the band structure of this design. The modal nature of this structure has previously been investigated by various parties [1]. We have extended this work to include a modal pictorial dictionary in which the nature of the modes can be readily identified as well as the R/Q's for each of the modes. Below 10GHz only monopole, dipole, quadrupole and sextupole bands exist for this particular structure. Herein we only consider the modal patterns of the bands themselves and have not included the beampipe modes in the pictorial dictionary. The R/Q definition that we use is that of [2]. In addition to the finite element simulations we also utilise a capacitive-inductive circuit model to achieve a rapid characterisation of the cavity.
    04/2012;
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    N. Juntong, R. M. Jones
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    ABSTRACT: The design of both higher order mode (HOM) and fundamental power (FP) couplers for a unique New Low Surface Field (NLSF) cavity is presented. Here we present a study which uses ILC baseline couplers. The Balleyguier method of calculating external quality factor is used and the results validated using both Microwave studio and HFSS.
    10/2011;
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    N. Juntong, R. M. Jones
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    ABSTRACT: We present an optimized geometry for a 1.3 GHz superconducting cavity in which the surface electromagnetic fields have been minimized and the bandwidth of the fundamental mode has been maximized. We refer to this design as the New Low Surface Field (NLSF) cavity. Earlier work focused on properties of the fundamental mode. Here we additionally study higher order modes (HOMs), means of damping them, and short range wake fields. A two-band circuit model is employed in order to facilitate rapid characterization of cavity HOMs. Comment: Presented at First International Particle Accelerator Conference, IPAC'10, Kyoto, Japan, from 23 to 28 May 2010
    06/2010;
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    ABSTRACT: We analyse higher order modes in the 3.9 GHz bunch shaping cavities recently installed in the FLASH facility at DESY. We report on recent experimental results on the frequency spectrum from probe based measurements made at CMTB at DESY. These are compared to those predicted by finite difference and finite element computer codes. This study is focused mainly on the dipole component of the multi-pole expansion of the wakefield.. The modes are readily identifiable as single-cavity modes provided the frequencies of these modes are below the cut-off of the inter-connecting beam pipes. The modes above cut-off are coupled to the 4 cavities and are distinct from single cavity modes Comment: Presented at First International Particle Accelerator Conference, IPAC'10, Kyoto, Japan, from 23 to 28 May 2010
    06/2010;
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    ABSTRACT: Contribution to a conf. proceeding (book/online)
    1st International Particle Accelerator Conference,Kyoto,Japan (2010),3007-3009.
  • [Show abstract] [Hide abstract]
    ABSTRACT: We anal­yse the high­er order modes in the 3.9GHz bunch shap­ing cav­i­ties re­cent­ly in­stalled in the XFEL/FLASH fa­cil­i­ty at DESY. We re­port on re­cent ex­per­i­men­tal re­sults on the fre­quen­cy spec­trum, both beam and probe based. These are com­pared to those pre­dict­ed by fi­nite el­e­ment com­put­er codes, glob­alised scat­ter­ing ma­trix cal­cu­la­tions and a two-band cir­cuit model. This study is fo­cused on the dipole com­po­nent of the multi­band ex­pan­sion of the wake­field.
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    Nawin Juntong
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    ABSTRACT: The main accelerating cavities of the ILC provide acceleration of both positron and electron beams to 250 GeV per beam and 500 GeV per beam in a proposed upgrade. The wake-fields excited by each ultra-relativistic beam in the accelerating cavities can cause appreciable dilution of the beam emittance. Each cavity is supplied with both fundamental and higher order mode couplers. The geometrical configuration of these rf couplers results in an asymmetrical field and this gives rise to both an rf kick being applied to the beam and a transverse wake- field. Detailed electromagnetic (e.m.) fields are simulated in the vicinity of the couplers in order to assess the impact on the beam dynamics for the ALICE/ERLP (1) couplers.