Mechanical study of 400 MHz prototype double quarter wave crab cavity for LHC luminosity upgrade Page: 3 of 5
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MECHANICAL STUDY OF 400 MHZ DOUBLE QUARTER WAVE CRAB
CAVITY FOR LHC LUMINOSITY UPGRADE*
B. P. Xiao", L. Alberty2, S. Belomestnykh13, I. Ben-Zvi'3, R. Calaga2, T. Grimm4, J. Skaritkal, Q.
Wu1.
1BNL, Upton, New York, USA
2CERN, Geneva, Switzerland
3Stony Brook University, Stony Brook, New York, USA
4Niowave, Inc., Lansing, Michigan, USA
Abstract The fundamental mode electro-magnetic field
distribution in the cavity is shown in Figure 2. TheA double quarter wave crab cavity has been
designed in Brookhaven National Lab for the Large
Hadron Collider (LHC) luminosity upgrade. A finite
element model software is used to simulate the
mechanical strength of this crab cavity. The results are
presented and a reinforcement design has been
proposed to meet the safety requirements. The
reinforcement components, as well as the cavity, are
fabricated and assembled at Niowave.
INTRODUCTION
The high luminosity upgrade of LHC requires
vertical and horizontal crabbing of the beams. To do
this, a double quarter wave superconducting RF crab
cavity has been designed by BNL and CERN. Its
prototype is fabricated by Niowave, Inc, and is under
preparations for vertical testing at BNL. The
mechanical strength safety requirements at both BNL
and CERN apply to this cavity.
Based on the simulations with a finite element
model using software ANSYSm, a solution for the
mechanical strength of this crab cavity has been
proposed, and a prototype design has been detailed. In
this paper we introduce the simulation results of the
prototype design.
CAVITY DESIGN
The RF design of the double quarter wave crab
cavity is introduced elsewhere [1], and its geometry is
shown in Figure 1. The cavity looks like a section of
coaxial structure, with its center conductor cut and
separated to form two capacitive plates, with a vertical
electric field in between at the fundamental mode, and
thus offers the crabbing voltage needed. Comparing to
the quarter wave version [2, 3], it is optimized to
cancel the on-axis accelerating (longitudinal) field and
to reduce the overall nonlinearity of the deflecting
voltage as a function of offset [1]. Some of the key
parameters of this cavity are listed in Table 1.
This work is supported by Brookhaven Science Associates,
LLC under Contract No. DE-AC02-98CH10886 with LARP and
the U.S. DOE, and supported by EU FP7 HiLumi LHC - Grant
Agreement 284404.
tbinping@bnl.govcenter capacitive plates
high electric field.are under low magnetic and
_ Qi;
Figure 1: Geometry of the double quarter wave cavity.
Table 1: Key parameters of the cavity.
Fundamental Mode Frequency [MHz] 400
Nearest Mode Frequency [MHz] 579
Vertical Deflection Voltage [MV] 3
Rt/Q (Fundamental Mode) [Ohm] 400
Epeak [MV/m] 44
Bpeak [mT] 60
Vacc [kV] 1.6
Stored Energy [J] 9
---
Figure 2: Electric field (left) and magnetic field (right)
of the fundamental mode.
MECHANICAL STUDY
Conditions
Based on the safety requirements at CERN and
BNL, with a relief valve set at 1.5 bar and safety
coefficient of 1.43/1.1, the cavity needs to pass a proof
test with maximum pressure of 2 bar outside the cavity
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Xiao, B.; Alberty, L.; Wu, Q.; Skaritka, J.; Belomestnykh, S.; Ben-Zvi, Ilan et al. Mechanical study of 400 MHz prototype double quarter wave crab cavity for LHC luminosity upgrade, article, May 12, 2013; United States. (https://digital.library.unt.edu/ark:/67531/metadc841205/m1/3/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.