LINAC2018 - List of Keywords (electromagnetic-fields)

Paper	Title	Other Keywords	Page
TUPO031	Investigation of the Surface Resistance of Niobium Between 325 MHz and 1300 MHz Using a Coaxial Half-wave Cavity	cavity, SRF, niobium, pick-up	395
	H. Park, S.U. De Silva, J.R. Delayen ODU, Norfolk, Virginia, USA
	The Center for Accelerator Science at Old Dominion University has built a half-wave coaxial cavity () to measure the surface resistance of niobium as a function of frequency, temperature, rf field, preparation techniques, over a wide range of frequencies of interest for particle accelerators. The characteristics of the half-wave coaxial cavity provide these information on a same surface. The preliminary results showed clearly the frequency dependence of residual surface resistance (). After establishing baseline, we have conducted a study of low temperature baking effect on the surface resistance under controlled environment. This paper will describe the details of the test procedure, results and we will explore underlying physics of the phenomenon. H. Park et al., MOPB003, Proc. SRF2015, http://jacow.org/ ** H. Park et al., THPB080, Proc. SRF2017, http://jacow.org/
	Slides TUPO031 [0.966 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO031
About •	paper received ※ 17 September 2018 paper accepted ※ 08 October 2018 issue date ※ 18 January 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPO035	Determination of the Field-dependence of the Surface Resistance of Superconductors from Cavity Tests	cavity, experiment, SRF, superconducting-cavity	405
	J.R. Delayen, S.U. De Silva, H. Park ODU, Norfolk, Virginia, USA
	Cryogenic tests of superconducting cavities yield an average surface resistance as a function of the peak surface magnetic field. An analytical formalism has been developed to extract the actual field dependence of the surface resistance from cavity tests and is applied to coaxial cavities and cavities of more complex geometries.
	Slides TUPO035 [0.524 MB]
	Poster TUPO035 [1.002 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO035
About •	paper received ※ 12 September 2018 paper accepted ※ 19 September 2018 issue date ※ 18 January 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPO053	Fabrication of Nb Mushroom Shaped Cavity for Evaluation of Multi-layer Thin-film Superconductor	cavity, vacuum, cryogenics, superconducting-cavity	454
	H. Oikawa Utsunomiya University, Utsunomiya, Japan K. Enami, H. Hayano, H. Inoue KEK, Ibaraki, Japan T. Higashiguchi Center for Optical Research and Education, Utsunomiya University, Utsunomiya, Japan
	The accelerating gradient of the Nb superconducting RF cavity seems to reach the limit due to the RF critical magnetic field of the Nb material. To obtain more higher gradient, there has been proposed a method of increasing an RF critical magnetic field of the cavity inner surface by coating of multi-layer thin-film superconductor. It is needed to demonstrate improvement RF critical magnetic field of the RF cavity coated with multi-layer thin-film superconductor. To optimize thin-film superconductor, sample tests are required. A cavity for sample test is necessary to produce a strong RF magnetic field parallel to the surface of the sample for evaluating RF critical magnetic field. For such a cavity, we designed a mushroom shaped cavity made of Nb which is operated in cryogenic temperature. Input and pick up antenna coupler are also designed electrically and mechanically. The connection design of sample plate and cavity bottom plate in superconducting state is also designed. The Nb mushroom shaped cavity is under fabrication. Fabrication method and status are reported in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO053
About •	paper received ※ 17 September 2018 paper accepted ※ 20 September 2018 issue date ※ 18 January 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPO009	Evaluation of 60pC Beam Performance at cERL Injector for ERL Based EUV-FEL	emittance, cavity, optics, space-charge	699
	T. Hotei Sokendai, Ibaraki, Japan R. Kato, T. Miyajima KEK, Ibaraki, Japan
	In order to compensate for the emittance which is increased by space charge in the low energy region, it is important to transport the beam as designed. Until now, we did not consider couplers in injector superdonducting cavities in optics design. But in this study, to improve optics matching and emittance compensation conditions for space charge dominated beam in cERL at KEK, we introduced a new 3D cavity model. We first investigated the influence of the couplers on electromagnetic field distribution. As a result, it was found that an asymmetric focusing force is generated by the influence of the couplers. It also became clear that the influence of the coupler kick on the optics significantly devastated the emittance compensation condition from the calculating including space charge. Furthermore, it was found that by optimizing the optics in consideration of the coupler kick, it is possible to improve the beam control accuracy and reduce the emittance in beam commissioning.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-THPO009
About •	paper received ※ 12 September 2018 paper accepted ※ 20 September 2018 issue date ※ 18 January 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

TUPO031

Investigation of the Surface Resistance of Niobium Between 325 MHz and 1300 MHz Using a Coaxial Half-wave Cavity

cavity, SRF, niobium, pick-up

395

H. Park, S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA

The Center for Accelerator Science at Old Dominion University has built a half-wave coaxial cavity (*) to measure the surface resistance of niobium as a function of frequency, temperature, rf field, preparation techniques, over a wide range of frequencies of interest for particle accelerators. The characteristics of the half-wave coaxial cavity provide these information on a same surface. The preliminary results showed clearly the frequency dependence of residual surface resistance (**). After establishing baseline, we have conducted a study of low temperature baking effect on the surface resistance under controlled environment. This paper will describe the details of the test procedure, results and we will explore underlying physics of the phenomenon.
* H. Park et al., MOPB003, Proc. SRF2015, http://jacow.org/
** H. Park et al., THPB080, Proc. SRF2017, http://jacow.org/

Slides TUPO031 [0.966 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO031

About •

paper received ※ 17 September 2018 paper accepted ※ 08 October 2018 issue date ※ 18 January 2019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPO035

Determination of the Field-dependence of the Surface Resistance of Superconductors from Cavity Tests

cavity, experiment, SRF, superconducting-cavity

405

J.R. Delayen, S.U. De Silva, H. Park
ODU, Norfolk, Virginia, USA

Cryogenic tests of superconducting cavities yield an average surface resistance as a function of the peak surface magnetic field. An analytical formalism has been developed to extract the actual field dependence of the surface resistance from cavity tests and is applied to coaxial cavities and cavities of more complex geometries.

Slides TUPO035 [0.524 MB]

Poster TUPO035 [1.002 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO035

About •

paper received ※ 12 September 2018 paper accepted ※ 19 September 2018 issue date ※ 18 January 2019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPO053

Fabrication of Nb Mushroom Shaped Cavity for Evaluation of Multi-layer Thin-film Superconductor

cavity, vacuum, cryogenics, superconducting-cavity

454

H. Oikawa
Utsunomiya University, Utsunomiya, Japan
K. Enami, H. Hayano, H. Inoue
KEK, Ibaraki, Japan
T. Higashiguchi
Center for Optical Research and Education, Utsunomiya University, Utsunomiya, Japan

The accelerating gradient of the Nb superconducting RF cavity seems to reach the limit due to the RF critical magnetic field of the Nb material. To obtain more higher gradient, there has been proposed a method of increasing an RF critical magnetic field of the cavity inner surface by coating of multi-layer thin-film superconductor. It is needed to demonstrate improvement RF critical magnetic field of the RF cavity coated with multi-layer thin-film superconductor. To optimize thin-film superconductor, sample tests are required. A cavity for sample test is necessary to produce a strong RF magnetic field parallel to the surface of the sample for evaluating RF critical magnetic field. For such a cavity, we designed a mushroom shaped cavity made of Nb which is operated in cryogenic temperature. Input and pick up antenna coupler are also designed electrically and mechanically. The connection design of sample plate and cavity bottom plate in superconducting state is also designed. The Nb mushroom shaped cavity is under fabrication. Fabrication method and status are reported in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO053

About •

paper received ※ 17 September 2018 paper accepted ※ 20 September 2018 issue date ※ 18 January 2019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPO009

Evaluation of 60pC Beam Performance at cERL Injector for ERL Based EUV-FEL

emittance, cavity, optics, space-charge

699

T. Hotei
Sokendai, Ibaraki, Japan
R. Kato, T. Miyajima
KEK, Ibaraki, Japan

In order to compensate for the emittance which is increased by space charge in the low energy region, it is important to transport the beam as designed. Until now, we did not consider couplers in injector superdonducting cavities in optics design. But in this study, to improve optics matching and emittance compensation conditions for space charge dominated beam in cERL at KEK, we introduced a new 3D cavity model. We first investigated the influence of the couplers on electromagnetic field distribution. As a result, it was found that an asymmetric focusing force is generated by the influence of the couplers. It also became clear that the influence of the coupler kick on the optics significantly devastated the emittance compensation condition from the calculating including space charge. Furthermore, it was found that by optimizing the optics in consideration of the coupler kick, it is possible to improve the beam control accuracy and reduce the emittance in beam commissioning.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-THPO009

About •

paper received ※ 12 September 2018 paper accepted ※ 20 September 2018 issue date ※ 18 January 2019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)