SRF2015 - List of Authors (Adolphsen, C.)

Paper	Title	Page
TUPB012	LCLS-II High Power RF System Overview and Progress	562
	A.D. Yeremian, C. Adolphsen, J. Chan, G. DeContreras, K. Fant, C.D. Nantista SLAC, Menlo Park, California, USA
	Funding: Work supported by DoE, Contract No. DE-AC02-76SF00515 A second X-ray free electron laser facility, LCLS-II, will be constructed at SLAC. LCLS-II is based on a 1.3 GHz, 4 GeV, continuous-wave (CW) superconducting linear accelerator, to be installed in the first kilometer of the SLAC tunnel. Multiple types of high power RF (HPRF) sources will be used to power different systems on LCLS II. The main 1.3 GHz linac will be powered by 280 1.3 GHz, 3.8 kW solid state amplifier (SSA) sources. The normal conducting buncher in the injector will use four more such SSAs. Two 185.7 MHz, 60 kW sources will power the photocathode dual-feed RF gun. A third harmonic linac section, included for linearizing the bunch energy spread before the first bunch compressor, will require sixteen 3.9 GHz sources at about 1 kW CW. A diagnostic line at 94 MeV, for tuning and characterizing the beam prior to acceleration through the rest of the linac, will contain an S-band transverse deflection cavity (TCAV) to time-resolve the energy spread of the beam. A 2.856 GHZ model 5045 pulsed klystron already existing at SLAC will be used to power the TCAV. A description and an update on all the HPRF sources of LCLS-II and their implementation is the subject of this paper
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

THPB007	A Study of Resonant Excitation of Longitudinal HOMs in the Cryomodules of LCLS-II	1073
	K.L.F. Bane, C. Adolphsen, A. Chao, Z. Li SLAC, Menlo Park, California, USA
	Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 The Linac Coherent Light Source (LCLS) at SLAC, the world's first hard X-ray FEL, is being upgraded to the LCLS-II. The major new feature will be the installation of 35 cryomodules (CMs) of TESLA-type, superconducting accelerating structures. It is envisioned that LCLS-II will eventually be able to deliver 300 pC, 1 kA pulses of beam at a rate of 1 MHz. At a cavity temperature of 2K, any heat generated (even on the level of a few watts) is expensive to remove. In the last linac of LCLS-II, L3–-where the peak current is highest–-the power radiated by the bunch in the CMs is estimated at 14 W (charge 300 pC option, rep rate 1 MHz). But this calculation ignores resonances that can be excited between the bunch frequency and higher order mode (HOM) frequencies in the CMs, which in principle can greatly increase this number. In this report we develop a theory of resonant build up. Then, using 500 numerically obtained modes over the frequency range 3–5 GHz, we estimate the probability of significant resonant build up in L3 of LCLS-II. The effects of small random bunch phase and charge errors will also be addressed.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

THPB008	RF Simulations for an LCLS-II 3rd Harmonic Cavity Cyromodule	1078
	L. Xiao, C. Adolphsen, Z. Li, T.O. Raubenheimer SLAC, Menlo Park, California, USA
	The FNAL designed 3.9 GHz third harmonic cavity for XFEL will be used in LCLS-II for linearizing the longitudinal beam profile. The 3.9 GHz SRF cavity is scaled down from the 1.3 GHz TESLA cavity shape, but has a disproportionately large beampipe radius for better higher-order mode (HOM) damping. The HOM and fundamental power (FPC) couplers will generate asymmetric field in the beam region, and thereby dilute the beam emittance. Meanwhile, due to the large beampipe, all but a few of the HOMs are above the beampipe cutoff. Thus the HOM damping analyses need to be performed in a full cryomodule, rather than in an individual cavity. The HOM damping in a 4-cavity cryomodule was investigated to determine possible trapped modes using the parallel electromagnetic code suite ACE3P developed at SLAC. The coupler RF kicks induced by the HOM and FPC couplers in the 3.9 GHz cavity were evaluated. A possible cavity-to-cavity arrangement is proposed which could provide effective cancellation of these RF kicks. In this paper we present and discuss the RF simulation results in the 3.9 GHz third harmonic cavity cryomodule. Work supported by Department of Energy under contract Number DE-AC02-76SF00515.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

THPB077	Modified TTF3 Couplers for LCLS-II	1306
	C. Adolphsen, K. Fant, Z. Li, C.D. Nantista, G. Stupakov, J. Tice, F.Y. Wang, L. Xiao SLAC, Menlo Park, California, USA I.V. Gonin, K. Premo, N. Solyak Fermilab, Batavia, Illinois, USA
	The LCLS-II 4 GeV SC electron linac will use 280 TESLA cavities and TTF3 couplers, modified for CW operation with input power up to about 7 kW. The coupler modifications include shortening the antenna to achieve higher Qext and thickening the copper plating on the warm section inner conductor to lower the peak temperature. Another change is the use a waveguide transition box that is machined out of a solid piece of aluminum, significantly reducing its cost and improving its fit to the warm coupler window section. This paper describes the changes, simulations of the coupler operation (heat loads and temperatures), rf processing results and CW tests with LCLS-II dressed cavities.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

Paper

Title

Page

LCLS-II High Power RF System Overview and Progress

562

A.D. Yeremian, C. Adolphsen, J. Chan, G. DeContreras, K. Fant, C.D. Nantista
SLAC, Menlo Park, California, USA

Funding: Work supported by DoE, Contract No. DE-AC02-76SF00515
A second X-ray free electron laser facility, LCLS-II, will be constructed at SLAC. LCLS-II is based on a 1.3 GHz, 4 GeV, continuous-wave (CW) superconducting linear accelerator, to be installed in the first kilometer of the SLAC tunnel. Multiple types of high power RF (HPRF) sources will be used to power different systems on LCLS II. The main 1.3 GHz linac will be powered by 280 1.3 GHz, 3.8 kW solid state amplifier (SSA) sources. The normal conducting buncher in the injector will use four more such SSAs. Two 185.7 MHz, 60 kW sources will power the photocathode dual-feed RF gun. A third harmonic linac section, included for linearizing the bunch energy spread before the first bunch compressor, will require sixteen 3.9 GHz sources at about 1 kW CW. A diagnostic line at 94 MeV, for tuning and characterizing the beam prior to acceleration through the rest of the linac, will contain an S-band transverse deflection cavity (TCAV) to time-resolve the energy spread of the beam. A 2.856 GHZ model 5045 pulsed klystron already existing at SLAC will be used to power the TCAV. A description and an update on all the HPRF sources of LCLS-II and their implementation is the subject of this paper

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

THPB007

A Study of Resonant Excitation of Longitudinal HOMs in the Cryomodules of LCLS-II

1073

K.L.F. Bane, C. Adolphsen, A. Chao, Z. Li
SLAC, Menlo Park, California, USA

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515
The Linac Coherent Light Source (LCLS) at SLAC, the world's first hard X-ray FEL, is being upgraded to the LCLS-II. The major new feature will be the installation of 35 cryomodules (CMs) of TESLA-type, superconducting accelerating structures. It is envisioned that LCLS-II will eventually be able to deliver 300 pC, 1 kA pulses of beam at a rate of 1 MHz. At a cavity temperature of 2K, any heat generated (even on the level of a few watts) is expensive to remove. In the last linac of LCLS-II, L3–-where the peak current is highest–-the power radiated by the bunch in the CMs is estimated at 14 W (charge 300 pC option, rep rate 1 MHz). But this calculation ignores resonances that can be excited between the bunch frequency and higher order mode (HOM) frequencies in the CMs, which in principle can greatly increase this number. In this report we develop a theory of resonant build up. Then, using 500 numerically obtained modes over the frequency range 3–5 GHz, we estimate the probability of significant resonant build up in L3 of LCLS-II. The effects of small random bunch phase and charge errors will also be addressed.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

THPB008

RF Simulations for an LCLS-II 3rd Harmonic Cavity Cyromodule

1078

L. Xiao, C. Adolphsen, Z. Li, T.O. Raubenheimer
SLAC, Menlo Park, California, USA

The FNAL designed 3.9 GHz third harmonic cavity for XFEL will be used in LCLS-II for linearizing the longitudinal beam profile. The 3.9 GHz SRF cavity is scaled down from the 1.3 GHz TESLA cavity shape, but has a disproportionately large beampipe radius for better higher-order mode (HOM) damping. The HOM and fundamental power (FPC) couplers will generate asymmetric field in the beam region, and thereby dilute the beam emittance. Meanwhile, due to the large beampipe, all but a few of the HOMs are above the beampipe cutoff. Thus the HOM damping analyses need to be performed in a full cryomodule, rather than in an individual cavity. The HOM damping in a 4-cavity cryomodule was investigated to determine possible trapped modes using the parallel electromagnetic code suite ACE3P developed at SLAC. The coupler RF kicks induced by the HOM and FPC couplers in the 3.9 GHz cavity were evaluated. A possible cavity-to-cavity arrangement is proposed which could provide effective cancellation of these RF kicks. In this paper we present and discuss the RF simulation results in the 3.9 GHz third harmonic cavity cryomodule.
Work supported by Department of Energy under contract Number DE-AC02-76SF00515.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

THPB077

Modified TTF3 Couplers for LCLS-II

1306

C. Adolphsen, K. Fant, Z. Li, C.D. Nantista, G. Stupakov, J. Tice, F.Y. Wang, L. Xiao
SLAC, Menlo Park, California, USA
I.V. Gonin, K. Premo, N. Solyak
Fermilab, Batavia, Illinois, USA

The LCLS-II 4 GeV SC electron linac will use 280 TESLA cavities and TTF3 couplers, modified for CW operation with input power up to about 7 kW. The coupler modifications include shortening the antenna to achieve higher Qext and thickening the copper plating on the warm section inner conductor to lower the peak temperature. Another change is the use a waveguide transition box that is machined out of a solid piece of aluminum, significantly reducing its cost and improving its fit to the warm coupler window section. This paper describes the changes, simulations of the coupler operation (heat loads and temperatures), rf processing results and CW tests with LCLS-II dressed cavities.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)