SCU Layout Concept -Minimal Segmentation

Joel Fuerst (ANL)

SCU 3-Lab Review MeetingDec. 16, 2014

SCU 3-Lab Review Meeting, Dec. 16, 2014

Introduction

“Segmentation” refers to the layout strategy for connecting an array of individual cryostats.

The downtime associated with removal of an individual cryostat is highly dependent on the layout.Component reliability and redundancy contribute to the expected frequency of cryostat removal.System cost increases with increased segmentation.

compared to

SCU 3-Lab Review Meeting, Dec. 16, 2014

Minimally segmented layout concept

Individual 5.5-m cryostats are arrayed in some number of continuous multi-cryostat strings.Strings are separated by 1 or 2 room-temperature self-seeding sections.Within a string, cryostat interconnect strategy is similar to the LCLS-II SC linac.The cryogenic distribution system is internal to the cryostats except at a warm bypass or at the cryoplant interface.

SCU 3-Lab Review Meeting, Dec. 16, 2014

Cryostat geometry

The vacuum vessel is standard 16” pipe.Thermal radiation shield is cooled by helium gas at ~50 K.Cold mass is cooled by saturated LHe at 4.3 K.Flanged sub-assemblies contain independent conduction-cooled current leads for each magnetic element.

Cold mass

Thermal shield

Vacuum vessel

Current lead/instrumentationassemblies

Retractable inter-cryostat vacuum bellows

SCU 3-Lab Review Meeting, Dec. 16, 2014

Cold mass geometry

Three 1.5-m SCU magnets plus quads, phase shifters, and bpms (not shown) are aligned to a rigid strongback.SCU magnet cooling channels are fed by a LHe reservoir pipe running the length of the string.Other elements are conductively cooled at 4.3 K.

Heliumpipe Magnet with

Horizontal field

SCU 3-Lab Review Meeting, Dec. 16, 2014

Alignment/subsystem access

Magnetic elements are precision aligned to the strongback. The cold mass assembly is suspended from the vacuum vessel using adjustable low-heat-leak supports. Cryostats can be independently aligned within a string due to flexible interconnect elements.Beam-based alignment is possible via x-y motion control systems located at the cold mass and/or the cryostat supports.Access to current leads, quads, phase shifters, bpms is possible via access ports in the vacuum vessel/thermal shield when the cryostat string is warm and vented.

SCU 3-Lab Review Meeting, Dec. 16, 2014

Refrigeration system

A cryogenic transfer line connects the refrigerator to the SCU string end boxes.Cryogenic bypasses are used at other warm sections.Static heat load of 2 W/m is a reasonable design goal.

UpstreamString 1

DownstreamString

UpstreamString 2

SurfaceTunnel

RefrigeratorColdbox

HeliumCompressors

Gas Storage

TransferLine

Bypass

SCU 3-Lab Review Meeting, Dec. 16, 2014

Refrigerator example

Some system components as well as buildings and utilities are pre-existing at SLAC.

SCU 3-Lab Review Meeting, Dec. 16, 2014

Summary

Factors affecting the choice of layout strategy include component reliability, maintainability, and cost. The minimal segmentation option can be summarized as follows:– Primary Advantage: Lower capital and operating system

costs are possible due to simpler cryostat geometry, the absence of a separate, external distribution system, and smaller refrigeration requirements.

– Primary Disadvantage: Removal of any individual cryostat requires a room-temperature thermal cycle of the entire undulator string.