# Presentation: 657131

## Undulator Development R&D Plan 

**Toshi Tanabe**
- George Rakowsky, John Skaritka, Steve Hulbert,
- Sam Krinsky, Timur Shaftan, and other NSLS-II Staff
*NSLS-II*
*NSLS-II Experimental Facilities Advisory Committee (EFAC)*
*2007/05/10-11*

## Outline

- Permanent Magnet Damping Wiggler
- Fanning angle reduction, damping effect adjustment
- Elliptically Polarized Undulator (EPU)
- 3 Pole Wiggler
- Cryo-Permanent Magnet Undulator (CPMU)
- Cold Measurement System
- New Magnet / Pole  Materials
- New Gap Separation Mechanism
- Superconducting Insertion Devices
- SCU, SCW and SEPU
- High Temperature Superconductor (HTS)

## 1) PM-Damping Wiggler

**W100**

**W80**

- CDR DW (w=100mm, Gap=15mm)
- Br=***1.35T***
- Integral of B2=0.1459 T2.m   (90.0% of ideal 1.8T sinusoidal field=0.162 T2.m)
- Keff/ = 2.71 mrad
- New Design with side magnets (w=80mm, Gap=12mm)
- Br=***1.30T***
- Integral of B2=0.1334 T2.m   (103% of ideal 1.8T sinusoidal field=0.1296 T2.m)
- Keff /  = 2.32 mrad

**Side Magnets**

## 2) EPU Comparison

- Apple-II,  HiSOR, and other types (Modified Apple-I, Crossed Undulator, etc.)  are being compared.

**Apple-II**

**HiSOR**

## 3) 3 Pole Wiggler

***3) 3 Pole Wiggler***

**16mm**

**17.5mm**

**Br=1.35T**
**Permendur Center Pole**
**Soft Iron (1006) Side Poles**
**Rectangular Magnets**

**S [mm]**

- Requirements:
- More than 2 mrad of radiation fan above 1T field
- Use standard gap dipole (35 mm Gap) chamber
- Fixed gap and removable from one side of the chamber
- Placed next to a BM   Cross talk issues are being investigated (3D model)

- Preliminary Magnetic Design

## 4) CPMU

**SPring-8 (Courtesy of T.Tanaka) **

**ESRF (Elettra Workshop 06)**** **

**Japanese/European Efforts on Cold Measurement System**

## New Materials for CPMU

***New Materials for CPMU***

**New Pole Materials**
-  Single Crystal Dy: Very high saturation flux density ~ 3.5T (if aligned)
-  Er-Ho-Dy alloy ~ 3T
- Vanadium permendur ~ 2.34T
- Soft iron ~ 2.1T

**Latest PrFeB Magnet **
-  New CR53 from Hitachi Metal

| Values at RT | P-53CR
(PrFeB) | 42AH
(NdFeB, used for MGU-25) |
| --- | --- | --- |
| Br [T] | 1.35 | 1.28 (Min) |
| Hcb [kA/m] | 1032 | 970 |
| Hcj [kA/m] | 1361 | 1909 |
| (BH)max [kJ/m3] | 349 | 318 |

**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 In-vacuum Gap Separation Mechanism

**Linear motors drive the outer cage.**

**Vacuum chamber**

**Rail **

## 5) Superconducting Insertion Devices

**Low Temperature Superconducting Undulator/ Wiggler**
- Test APC-NbTi wire

**Low Temperature**** ****Superconducting EPU**
- Design study, especially winding technique

**High Temperature SC Devices**
- Rapid conductor development in the industry
- 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

**YBCO HTS tape undulator**

**MgB****2**** etched conductor pattern**

## Latest Result

**High Temperature SCU proto type**
- Siemens HTS 5cm wide YBCO tape slotted (14mm period)  is immersed in LN (77K).
- Only one layer, one array, measured at 2mm away from the poles.

## Superconducting Wiggler

- CDR-SCW
- 17 pole @ 6.0T (u=6.0cm, gpole=15.0mm)
- Kpeak = 33.6
- Critical Photon Energy = 35.9 keV
- Total Power = 102.6 kW
- Peak on-axis angular power density = 36.7 kW / mrad

***With 1006 Steel, ***
***Required Current Density =****** 1300 A / mm******2***

**Too much for conventional**
**NbTi wire**

## Summary

- DW may require further refinement to reduce the impact on the ring.
- Tracking study with realistic field map is underway.
- More tracking studies are required for optimal structure of EPU for NSLS-II.
- 3 pole wiggler will be conventional PM device, however;
- Magnetic interaction with adjacent magnets should be taken into account.
- Residual dispersion due to asymmetric beta function at the location has be to minimized.
- Development of accurate cold field measurement system is essential for successful operation of CPMU.
- New materials to be developed for higher performance
- New gap separation mechanism to simplify the structure
- SC insertion devices planned for NSLS-II require further R&Ds.