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Title: BRIDGE-COUPLER THERMAL/STRUCTURAL ANALYSIS AND RESONANT FREQUENCY SHIFT STUDIES FOR THE SNS CCL

Abstract

No abstract prepared.

Authors:
Publication Date:
Research Org.:
Los Alamos National Lab., NM (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
783310
Report Number(s):
LA-UR-01-3207
TRN: US0110541
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: Conference title not supplied, Conference location not supplied, Conference dates not supplied; Other Information: PBD: 1 Jun 2001
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; SPALLATION; NEUTRON SOURCES; LINEAR ACCELERATORS; AUXILIARY SYSTEMS; THERMAL ANALYSIS; MECHANICS

Citation Formats

Z. CHEN. BRIDGE-COUPLER THERMAL/STRUCTURAL ANALYSIS AND RESONANT FREQUENCY SHIFT STUDIES FOR THE SNS CCL. United States: N. p., 2001. Web.
Z. CHEN. BRIDGE-COUPLER THERMAL/STRUCTURAL ANALYSIS AND RESONANT FREQUENCY SHIFT STUDIES FOR THE SNS CCL. United States.
Z. CHEN. Fri . "BRIDGE-COUPLER THERMAL/STRUCTURAL ANALYSIS AND RESONANT FREQUENCY SHIFT STUDIES FOR THE SNS CCL". United States. doi:. https://www.osti.gov/servlets/purl/783310.
@article{osti_783310,
title = {BRIDGE-COUPLER THERMAL/STRUCTURAL ANALYSIS AND RESONANT FREQUENCY SHIFT STUDIES FOR THE SNS CCL},
author = {Z. CHEN},
abstractNote = {No abstract prepared.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Jun 01 00:00:00 EDT 2001},
month = {Fri Jun 01 00:00:00 EDT 2001}
}

Conference:
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  • The Spallation Neutron Source (SNS) is an accelerator-based neutron scattering research facility. The linear accelerator (linac) is the principal accelerating structure and divided into a room-temperature linac and a superconducting linac. The normal conducting linac system that consists of a Drift Tube Linac (DTL) and a Coupled Cavity Linac (CCL) is to be built by Los Alamos National Laboratory. The CCL structure is 55.36-meters long. It accelerates H- beam from 86.8 Mev to 185.6 Mev at operating frequency of 805 MHz. This side coupled cavity structure has 8 cells per segment, 12 segments and 11 bridge couplers per module, andmore » 4 modules total. A 5-MW klystron powers each module. The number 3 and number 9 bridge coupler of each module are connected to the 5-MW RF power supply. The bridge coupler with length of 2.5 {beta}{gamma} is a three-cell structure and located between the segments and allows power flow through the module. The center cell of each bridge coupler is excited during normal operation. To obtain a uniform electromagnetic filed and meet the resonant frequency shift, the RF induced heat must be removed. Thus, the thermal deformation and frequency shift studies are performed via numerical simulations in order to have an appropriate cooling design and predict the frequency shift under operation. The center cell of the bridge coupler also contains a large 4-inch slug tuner and a tuning post that used to provide bulk frequency adjustment and field intensity adjustment, so that produce the proper total field distribution in the module assembly.« less
  • The mechanical design of the vacuum pumping systems for SNS DTL (Drift Tube Linac) and CCL (Cavity Coupled Linac) linac systems is summarized. Both vacuum systems were modeled to select the optimal pump configuration. The pressure history in up to 182 sub-volumes was analyzed in detail. Included in the model are time-dependent outgassing rates and pressure-dependent pump speeds for a variety of gas species. With this information, we solved for the pressure history during roughing and with turbo and ion pumps. The number and size of each pump were optimized to achieve the desired pressure with minimal costs. In themore » optimized design, directly mounted ion pumps were provided for six DTL tanks. For four CCL modules (each in length of 12-15 m), ion pumps with manifolds were selected. With all metallic surface outgassing, seal leakage and expected gas loads from all diagnostic devices taken into account, the designed systems can provide operating drift-tube pressure below 1.8 x 10{sup -7} Torr and CCL beamline pressures below 9.2 x 10{sup -8} Torr even under abnormal conditions. Details of the design and the modeling results are presented.« less
  • Los Alamos National Laboratory is responsible for the design of the room-temperature linac for the Spallation Neutron Source (SNS). This linac consists of a Coupled-Cavity Linac (CCL) and a Drift Tube Linac (DTL). During normal operation, about 80% of the Radio Frequency (RF) power is dissipated in the DTL cavity walls. This waste heat causes the cavities to expand, causing shifts in their RF resonant frequency. The DTL relies on the water cooling system to compensate for the frequency shift caused by RF heating. To guide the design of the cooling system and the frequency control scheme, thermal expansion andmore » frequency shift studies for several DTL cells are performed via numerical simulations. Temperature distributions and thermal deformations resulting from RF heating are evaluated separately for the tanks and 22 drift tubes using finite element models. The frequency shift of these cells are then computed based on the calculated deformations. Size and locations of the cooling channels are designed accordingly to provide adequate cooling and minimize frequency shift. The tank finite element model used to predict the tank temperature profile is benchmarked against experiment data.« less
  • In contrast to a normal conducting RF cavity, a superconducting RF cavity is very susceptible to shifts in its resonance frequency. The main sources of the shift are Lorentz force detuning and microphonics. In SNS, to compensate for the frequency shift, a feedforward control is to be applied. In this paper, as an initiative step, a frequency shift observer is proposed which is simple enough to be implemented with a digital signal processor in real time. Simulation results of the proposed frequency shift observer show reliable performance and acceptable computation time for the real time implementation.