# Presentation: 706570

## NSLS-II Insertion Device R&Ds

_**Toshi Tanabe**_
- George Rakowsky, John Skaritka and
- Susila Ramamoorthy
*NSLS-II Experimental Facilities Advisory Committee (EFAC)*

## Outline

- Cryo-Permanent Magnet Undulator (CPMU)
- New Magnet / Pole  Materials
- Cold Measurement System
- New Gap Separation Mechanism
- In-vacuum Elliptically Polarized Undulator (IVEPU)
- Superconducting Insertion Devices
- EPU
- High Temperature Superconductor (HTS)
- Cold Gas Refrigeration System
- International Collaborations
- Undulator Laboratory in Bldg. 832

## 1) CPMU

- IVU

- Remanence

- Coercivity

***1) CPMU***

**Cryo-Permanent Magnet Undulator** (Hara, *et. al*, 2004)
*Simple Concept*: NdFeB has a negative thermal coefficient of remanent field (Br) [-0.1 % / K@20oC], and of intrinsic coercivity (Hcj) [-0.5% / K@20oC ]
*PrFeB *(53CR at NEOMAX) shows no “spin canting” at the lower temperature.  However, it does not have high enough coercivity at the high temperature needed for baking.

**Notes:**
Let me show the magnetic performance of permanent magnets at low temperatures.
We measured  remanent field and coercivity of five different materials, 
Neodymium type, 27VH and 35EH with high coercivity but low remanence,
48H and 50BH with low coercivity but high remanence,
and praseodymium type, 53CR, special material developed for low temperature use.

First, let me show the remanent field.
In case of neodmium materials, there is a turning temperature around 140 K and the magnetic field starts decreasing below this temperature due to the spin reorientation. 
In contrast, the remanent field of 53CR shows monotonic increase at low temperatures.
50BH shows the highest field of 1.58 T around 140 K.

Next, coercivity.
Differently from the remanent field performance, the coercivity of all the magnets shows monotonic increase at low temperatures, 
The blue zone in the figure shows the area allowed for IVUs.
You can see at room temperature 48H, 50BH and 53CR cannot used for IVUs, however,
below 200 K, they are all available.
Accordingly, we have obtained a special permanent magnet, 50BH at 140 K, having both high remanent field and high coercivity.

53CR is the best material when used at low operating temperature below 77 K in combination with dysprosium pole or high temperature superconductor.  

Generally, the magnet having high coercivity shows good radiation resistance.
In the next figure, let me show the radiation damage at low temperatures.

## New Materials

***New Materials***

**W. Swift and M. Mathur**
**IEEE Trans. Mag. Vol.10, No.2 (1974)**

**Bakable PrFeB Magnet**
-  High Hcj type which can withstand the baking temperature (>100 °C)
- Get manufacturer/university with production capability involved
**Crystalized Dysprosium Pole**
-  Very high saturation flux density ~ 3.5T
- Vanadium permendur ~ 2.3T
- Soft iron ~ 2.1T
- A few vendors identified
- International collaboration subject

**Notes:**
Let me show the magnetic performance of permanent magnets at low temperatures.
We measured  remanent field and coercivity of five different materials, 
Neodymium type, 27VH and 35EH with high coercivity but low remanence,
48H and 50BH with low coercivity but high remanence,
and praseodymium type, 53CR, special material developed for low temperature use.

First, let me show the remanent field.
In case of neodmium materials, there is a turning temperature around 140 K and the magnetic field starts decreasing below this temperature due to the spin reorientation. 
In contrast, the remanent field of 53CR shows monotonic increase at low temperatures.
50BH shows the highest field of 1.58 T around 140 K.

Next, coercivity.
Differently from the remanent field performance, the coercivity of all the magnets shows monotonic increase at low temperatures, 
The blue zone in the figure shows the area allowed for IVUs.
You can see at room temperature 48H, 50BH and 53CR cannot used for IVUs, however,
below 200 K, they are all available.
Accordingly, we have obtained a special permanent magnet, 50BH at 140 K, having both high remanent field and high coercivity.

53CR is the best material when used at low operating temperature below 77 K in combination with dysprosium pole or high temperature superconductor.  

Generally, the magnet having high coercivity shows good radiation resistance.
In the next figure, let me show the radiation damage at low temperatures.

## Cold Measurement System

**Cold In-Situ Field Measurement**

- In-vacuum mapper with Hall probe.  The postion accuracy is maintained by laser tracker and piezo controller.

**In-vacuum streched wire / pulse wire system are**
**also in consideration**

## New In-vacuum Gap Separation Mechanism

**Linear motors drive the outer cage.**

**Vacuum chamber**

**Rail **

## 2) In-Vacuum EPUs

**Out-of-vacuum Device** (Gmag~10mm)
- Apple-II : bigger tuning range, simpler structure
- HiSOR EPU: easier shimming and more benign field profile

**Apple-II**

**HiSOR**

**In-vacuum Helical Undulator at SP8**

***In-vacuum Device**** (G**mag**~7mm)*

## 3) Superconducting Insertion Devices

**Low Temperature Superconducting Undulator**
- Different techniques are being tested all over the world
- Need more R&Ds such as thermal intercept designs and lead design, etc. to achieve stable operations in a ring

**Superconductor EPUs**
- Various designs have been proposed
- Available only after the development for a linear device is established

**High Temperature SC Device**
- Depends on the conductor development
- New type such as coated conductor and thin film available  _*More design flexibility*_
- Once the conductor exceeds the necessary performance level, it will be very promising candidates for future IDs

## SC-EPUs and a HTS Undulator

- Sasaki Snake

- S. Chouhan

- Rossmanith

- HTSU by T.Tanabe

## 4) Cold Gas Refrigeration System

- Use of LHe creates many safety issues to deal with.

- Closed circuit He refrigerator alleviates these problems.

- LHe plant may not be available in the vicinity of the ID.

- Needs higher capacity and more reliability for NSLS-II devices (CPMUs and SCUs)

## Schedule

- 2007

- 2008

- 2009

- 2011

- 2010

- 2012

- 1st user beam

## Summary

- _Cold measurement system_ is essential for the CPMU baseline design
- New in-vacuum gap separation mechanism
- _New material R&Ds_ for further enhancement of the CPMU performance
- _In-vacuum EPU_ design will be a challenge, but it shares the many development aspects with in-vacuum gap separation mechanism.
- _SCU R&Ds_
- Low temperature SCUs still require R&Ds
- _SC-EPU_ will be available once the technology for linear devices matures
- _HTS versions_ are promising candidates in the future
- _Circulating He gas cooling system_ needs to be developed
- International Collaborations
- Undulator Laboratory in Bldg. 832