# Presentation: 226803

## Superconducting UndulatorsAreas of risk and Associated R&D

- Physics requirements:
- Field and period defined by the experiment
- Operational modes
- Main engineering concerns:
- Magnet design
- Defining geometry
- Selecting conductor
- Designing protection system
- Providing field tuning method
- Cryogenic design
- Sources of heat
- Mechanical aspects
- Cryocooler based system
- Integration with synchrotron ring
- Magnet system
- Cryogenics / vacuum chamber
- Review of critical issues

## Magnet design issues

- Define geometry (coilpack, yoke, and pole) based on selected period and gap
- May consider different pole materials
- Most efficient (optimal) geometry maximizes Bcenter/Bcond, independent of conductor choice!
- Select conductor based on
- Jc(B,T) (Must provide the Jeng required to produce center field, with Jsc/Jc<1)
- coilpack geometry (conductor size, insulation, current, winding method)
- Trade-off between higher current (lower ins. Filling factor, larger heat load from leads) and higher inductance (increased internal voltages, higher peak temp. during quench)
- Stability (Cu:SC, RRR, Deff, etc), protection considerations (Cu:SC, RRR, L, Etot)
- Protection
- Want passive system
- Passive system implies that Etot will be deposited “cold” during quench (anticipate E~1500J/period)
- Need quench detection to shut off power supplies
- Field tuning
- Need to determine tolerance requirements on machined parts; tolerances on winding
- Roll-off must meet ring requirements; roll-off “profile” varies with current
- Provide (static or dynamic) tuning method to guarantee the ability to meet field quality

## Cryogenic design

- Must consider different sources of heat deposition:
- Magnet itself
- Conduction loads due to magnet supports
- Conduction loads from current leads
- “Generic” radiation load from 80K shield
- Ohmic heating from any joints
- Warm-cold vacuum transitions
- Conduction loads through RF transitions
- “Generic” radiation from upstream/downstream warm vacuum chamber
- RF (Ohmic) heating of cold beam-tube
- Must know magnitude of heat load, and resulting temperature distribution
- Radiation load from upstream SR sources
- Must know magnitude and distribution along beam-tube; different “spurious” conditions and their frequency
- Mechanical aspects
- Thermal contraction of beam-tube must be dealt with “internally”
- Magnet support design should allow for zero transverse displacement during cooldown
- System must not require users to supply helium on a regular basis
- Cryocooler design
- Use superbends as example
- consider using cryocoolers as liquifiers in closed cycle to reduce/eliminate temperature gradients?

## Integration with Synchrotron ring

- Magnet system
- Must meet roll-off and field integral requirements (need detailed magnetic measurements)
- Ramp-rate must be compatible with the experiment
- Vacuum chamber / cryogenics
- Need to understand behavior of 4.2K vacuum chamber in ring
- Must provide RF continuity through transition region
- Cold bore vacuum chamber should be designed to function at room temp. also
*A key parameter in both is the allowable gap:*
*	**- gap affects magnet design: (B(J); roll-off; geometry*
*	**- affects cryogenics: RF heating; SR heating from upstream*

## Summary of critical issues

- “Input” parameters
- Period, gap, required field
- Basic coilpack and yoke/pole design to attain field		(LDRD; industry)*
- Quench protection system				(LDRD; industry)*
- Field quality
- Machining and winding tolerances			(paper study; LDRD; industry)
- Field tuning mechanism				(R&D)
- Measurement system				(R&D; industry)
- Cryogenics
- “generic” loads				(conventional)
- Warm-cold transitions				(R&D; industry)
- RF loads					(R&D)
- Synchrotron radiation loads from upstream sources		(can be estimated; measure)

- Black: engineering know-how exists, but may have significant risk
- Blue: significant concern; significant LBL involvement
- Red: critical issue that we must address in-house
- Green: R&D not essential to ALS device

- *assuming the basic magnet design does not push the limits of conductors