# Presentation: 161400

## CESR super-conducting damping Wigglers

- Alexander Temnykh for CESR operating group

- BNL NSLS meeting, 6/1/06

- D. Rice
- D. Rubin
- J. Crittenden
- S. Chapman
- J. Codner
- R. Gallagher
- Y. He
- J. Kandaswamy

- V. Medjidzade
- A. Mikhailichenko
- N. Mistry
- T. Moore
- E. Nordberg
- S. Richichi
- E. Smith
- K Smolenski
- W. Trask

## General Information

- Choice of  the main parameters:  peak field, length, period, technology, magnetic design
- Production,  magnetic field measurement, quality control and cost.

- BNL NSLS, 6/1/06

- A. Temnykh

## General Information   

- 2.1T peak field, 40cm period, 20cm pole width, 7.62cm gap, 9x5cm beam clearance
- 8 poles (asymmetric magnetic design)
- Iron poles & superconductive coils (superferric technology)
- Cryogenic performance:
-       ~1.3W at 4K and ~40W at 77K
- Wigglers used to:
- Enhance radiation damping
- control beam emittance

- 2 wiggler cluster in ring

- BNL NSLS, 6/1/06

- A. Temnykh

**Notes:**
Before going through many details of our experience I would like to remind you main characteristics of CESRc wiggler magnets.
CESRc wigglers have 2.1T maximum field, 40cm period, 1.3m length
Asymmetric magnetic design ( 8 poles)
Made with superfferic technology, iron poles and superconductin coils.
And we using them to enhance radiation damping at low 1.8GeV/ beam energy.
On picture you can see 2 wigglers cluster in tunnel. In fact you see cryostats, magnets are inside. 

## General Information   

- Cold mass

- Cryostat cross-section

- BNL NSLS, 6/1/06

- A. Temnykh

**Notes:**
Before going through many details of our experience I would like to remind you main characteristics of CESRc wiggler magnets.
CESRc wigglers have 2.1T maximum field, 40cm period, 1.3m length
Asymmetric magnetic design ( 8 poles)
Made with superfferic technology, iron poles and superconductin coils.
And we using them to enhance radiation damping at low 1.8GeV/ beam energy.
On picture you can see 2 wigglers cluster in tunnel. In fact you see cryostats, magnets are inside. 

## Setting the main parameters: peak field and total length

- Active length (Lw) should be enough to provide damping rate: 1/ ~ 30 sec-1 => Lw ~ 18m
- Period: Longer period results in weaker cubic non-linearity, but increases orbit excursion which increase sensitivity to field non-uniformity across wiggler poles. Reasonable compromise:  ******cm**

- Setting the main parameters: peak field and total length

- Expected field non-uniformity for 20cm pole width and 7 cm gap

- BNL NSLS, 6/1/06

- A. Temnykh

**Notes:**
Transition with wigglers is different. If we assumed that the most radiation coming from wiggler, the damping rate will be proportional to field in square multiplied by the wigglers length, horizontal beam emittance  ....

In our case because we have limit on beam energy spread ~ 8e-4. It gives the maximum wiggler field  ~ 2.1T. To recover reasonable damping rate ~30Hz the total lentgh ~ 18m.  

## Setting the main parameters: technology

- Normal conducting copper/iron. Similar sized magnets required ~300kW/wiggler.
- Permanent magnet (NdFeB). 2T in 5cm x 9cm gap difficult, BIG magnets, $$, must be opened or removed for 5GeV running.
- Superferric  technology (iron poles & superconducting coils) only viable option for high (2T) fields over given beam aperture.

- Setting the main parameters: technology

- From D.Rice presentation: CESR-c Wiggler Manufacture - PAC 2003

- BNL NSLS, 6/1/06

- A. Temnykh

**Notes:**
Technology choice.

It was obviouse that the magnet length should be ~ 1.5m and good field region ~5x9cm, we need 12-14 units in ring.
 1) If we build normal conducting iron/copper magnet it will require  ~300kW power. It would be difficult to fit it tunnel. 

2) Permanent magnet. To provide 2T field in big  5 x 9 cm gap need a lot of magnetic material, which is very expensive. The second complication is that 50% of time we operating at high 5GeV energy, during this operation magnets should be removed.

3) Superferric technology (iron poles and superconducting coils was most suitble for us. It gives high field in big gap and low power consumption. We had some experience at that time already.     

## Setting the main parameters: type of symmetry 

- Field along
- magnet

- Beam
- trajectory

|  | 7 poles (symmetric) | 8 poles (asymmetric) |
| --- | --- | --- |
| Poles length [cm] | 15+20+20+20+20+20+15 = 130 | 10+15+20+20+20+20+15+10 = 130 |
| Bmax/pole  [T] | -1.6/2.1/-2.1/2.1/-2.1/2.1/-1.6 | -1.1/2.1/-2.1/2.1/-2.1/2.1/-2.1/1.1 |

- Setting the main parameters: type of symmetry

- BNL NSLS, 6/1/06

- A. Temnykh

**Notes:**
Type Symmetry choice.

We considered symmetric, 7 pole, and asymmetric 8 pole magnetic design. Plots show field along magnet and beam trajectories. 

## Setting the main parameters: type of symmetry 

- Cubic non-linearity (vertical) 5% smaller for fixed damping
- Only 2 types of poles (vs. 3)
- Asymmetric design (8 poles)
- Horizontal orbit excursion two times smaller
- Integrated magnetic field quality is not sensitive to systematic errors on in poles.
- Maintains linearity over wider range of excitation levels

- Units 1 & 2 are 7-pole,  units 3 and up are 8-pole. We built 16 units total

- Setting the main parameters: type of symmetry

- BNL NSLS, 6/1/06

- A. Temnykh

**Notes:**
Here is the list of arguments for 7 and 8 pole design.
....
Finally after we we built one 7 pole magnet and tested it with beam we switched to 8 pole configuration.

## Production: Coil Winding

**Coils are wound directly on individual machined iron poles.**
**Main poles 660 turns, 0.75 mm, 70 filament wire**
**Wet wound with Epotek T905******** epoxy**
**Clamped with shim****blocks every 5 layers****to maintain mechanical****tolerances.**
**Experienced winder****produces 1/day**

- Beam axis

- From D.Rice presentation: CESR-c Wiggler Manufacture - PAC 2003

- BNL NSLS, 6/1/06

- A. Temnykh

**Notes:**
Here are some details of coil winding.

## Production: Coil Winding

- From D.Rice presentation: CESR-c Wiggler Manufacture - PAC 2003

- BNL NSLS, 6/1/06

- A. Temnykh

**Notes:**
And coil winding setup.

## Magnetic field measurement: field mapping with Hall probe 

- Difference between measurement and calculation

- By(z),  Hall probe measurement and model calculation

- Magnetic field measurement: field mapping with Hall probe

- BNL NSLS, 6/1/06

- A. Temnykh

**Notes:**
Hall probe magnetic measurement example. Good consistence with calculation, left plot, but because of spread in the region with high gradient, accuracy not enough to measure field integrals. For this we used stretched coil techniques

## Magnetic field measurement: field integrals measurement with stretched coil

- First integral with straight coil:

- Second integral with twisted coil:

- BNL NSLS, 6/1/06

- A. Temnykh

**Notes:**
Measure first integral with strait coil and second with twisted

## Magnetic field measurement: wiggler #1(7pole) stretched coil measurement

- BNL NSLS, 6/1/06

- A. Temnykh

## Magnetic field measurement: wiggler #4(8pole) stretched coil measurement

- BNL NSLS, 6/1/06

- A. Temnykh

## Production: pole quality control

- Check for missing turns
- Turn-to-turn shorting

- Production: pole quality control

- Warm  magnetic field measurement setup for pole testing,  Imax~ 1A.

- BNL NSLS, 6/1/06

- A. Temnykh

**Notes:**
Quality control illustration.
The key for good magnetic field quality in asymmetric design is pole-to-pole uniformity. To provide control for this we used warm magnetic measurement.
Setup is shown on picture.

## Production: quality controlshorts, missing turns checking

- Bad pole, 2 layers (40turns) shorted

- Warm magnetic measurement: "z" scan ( along beam axis)

- BNL NSLS, 6/1/06

- A. Temnykh

**Notes:**
Example of warm magnetic measurement.
From magnetic field profile difference we estimated difference in geometry and used it for pole sorting. 

## Production: quality controla1 - problem

- Production: quality controla1 - problem

- Explanation: variation in coil geometry

- Unit #

- BNL NSLS, 6/1/06

- A. Temnykh

**Notes:**
Example of warm magnetic measurement.
From magnetic field profile difference we estimated difference in geometry and used it for pole sorting. 

## Production: quality controla1 - problem

- Two peaks at the pole ends indicated that tested pole -0.4mm narrower than "reference".

- "x" scan ( across beam axis)

- Warm magnetic measurement: "x" scan

- BNL NSLS, 6/1/06

- A. Temnykh

**Notes:**
Example of warm magnetic measurement.
From magnetic field profile difference we estimated difference in geometry and used it for pole sorting. 

## Wiggler a1 component effect on coupling One wiggler (Oct 2002) and 12 wiggler (Jan 2005) optics

- Nov 2002, One wiggler (#1) optics.
- Wave analysis indicated coupling source ( ~ 2Gm/cm) at wiggler location, ~1.5Gm/cm from magnetic measurement.

- Jan 2005, 12 wigglers optics.
- Wave analysis indicated no coupling source at wigglers location.

- BNL NSLS, 6/1/06

- A. Temnykh

## Production: resources and cost 

- Sr. Technical & Supervisory: **5.0** FTE
- Technical support:	           **13** FTE
- Approximate cost per wiggler unit for parts and outside machining and manufacturing below $100k
- Results in production of one wiggler every ~3 weeks

- Production: resources and cost

- BNL NSLS, 6/1/06

- A. Temnykh

**Notes:**
Cost

## Conclusion

- We have built 16 superferric wigglers, 12 of them have been installed in the ring and now under operation.
- Beam based wiggler characterization is in good agreement with model.
- We have good wigglers and reliable  model
- So far, we have not seen beam performance degrading  due to wiggler field nonlinearities.
- Very positive experience.

- BNL NSLS, 6/1/06

- A. Temnykh

## Magnetic measurement summary.

- Units 1 and 2 are 7-pole, units 3 and up are 8-pole

- BNL NSLS, 6/1/06

- A. Temnykh

## #6 norm

- #6 skew

- #8 norm

- #10 norm

- #7 norm

- #9 norm

- #11 norm

- #7 skew

- #8 skew

- #9 skew

- #10 skew

- #11 skew

- BNL NSLS, 6/1/06

- A. Temnykh

## #12 norm

- #12 skew

- #13 skew

- #14 skew

- #16 skew

- #15 skew

- #9' skew

- #14 norm

- #16 norm

- #13 norm

- #15 norm

- #9' norm

- BNL NSLS, 6/1/06

- A. Temnykh

## Wiggler characterization with beam and model benchmarking.

- Streak camera measurement

- Bunch length and beam energy spread

- BNL NSLS, 6/1/06

- A. Temnykh

## Wigglers characterization with beam and model benchmarking 

- Wigglers characterization with beam and model benchmarking

- BNL NSLS, 6/1/06

- A. Temnykh

## Wiggler characterization with beam and model benchmarking 

- +- 10mm

- Wiggler characterization with beam and model benchmarking

- Tune variation with beam position in 18E cluster (3wigglers).

- BNL NSLS, 6/1/06

- A. Temnykh

## Wiggler characterization with beam and model benchmarking

- Vertical and horizontal tunes measured as a function of horizontal orbit position in wigglers

- BNL NSLS, 6/1/06

- A. Temnykh

## Wiggler characterization with beam and model benchmarking 

- Vertical and horizontal tunes measured as a function of horizontal orbit position in wigglers

- Wiggler characterization with beam and model benchmarking

- BNL NSLS, 6/1/06

- A. Temnykh

## Wiggler characterization with beam and model benchmarking 

- Wiggler characterization with beam and model benchmarking

- Shaker

- Receiver

- Phase shifter
- + Amplifier

- Tune tracker provides beam resonance shaking with stable amplitude horizontal/vertical plane.

- BPM (amplitude)

- Tune tracker
- (tune)

- BNL NSLS, 6/1/06

- A. Temnykh

## Wiggler characterization with beam and model benchmarking.

- Measured and calculated dependence of vertical/horizontal tune versus vertical/horizontal amplitude

- BNL NSLS, 6/1/06

- A. Temnykh