nlc - the next linear collider project nlc january video conference status of permanent quadrupoles...

NLC - The Next Linear Collider Project

NLC January Video conference

Status of Permanent Quadrupoles

James T VolkJanuary 18, 2001


NLC Quad Specifications

Table I SpecificationsItem valueAperture 12.7 mmQuantity Length 288 324 mm

399 432 mm576 965mm

Maximum Pole tip field 0.62 Tesla for 324 mm0.80 Tesla for others

Adjustment + 0 to – 20%Temperature Stability 0.5% at 25 1 oCHigher Harmonics b3/b2 < 0.02Field Accuracy 0.5% at any field valueCenter Location Magnetic to Fiducial 0.1 mmCenter Stability 0.001 mm over range of adjustment


Corner tuner

Rods rotate to adjust field

Rotating tuning rods

Permanent magnets

Pole


Wedge QuadRods rotate to adjust field

Rotating magnets Wedge Magnets

Pole


SSW and Wedge Quad

Wire stages


Gradient ((measured-average)/average)*10000

FWSQ001-2

0

5

10

15

20

25

30

-5 -4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 More

units

FWHM 3 units


Center StabilityDifference between 5 successive measurements

FWSQ001-2

0

10

20

30

40

50

60

x center microns

FWHM 2 microns


Calculated vs.Measured Field

• PANDIRA predicts 0.62 Tesla at 0.005 m for 0.202 m• This is 25.05 Tesla• SSW measures 21.02 Tesla• 16% lower than predicted• Br and Hci in calculation needs to be adjusted


FWSQ001

• Close to desired field 16 % low

• Have 20% tunable range

• Need to measure Center stability during adjustment

• The FNAL test stand is capable of these measurements

• New wedge tuner design in drafting magnet material on order

• Increase the amount of magnet material by 15% increased predicted field by 25%


Status of permanent “wedge” magnet measurements at SLAC, Jan 2001,pg 1/2

• Tuner rods much harder to rotate than expected– Chain drive mechanism was modified but still one rod rotated by 6

- 8 degrees more than other 3, so resorted to no chains, rotate each rod by hand and clamp in place with special plate. If we have the rod starting positions correct, then we have the rotated the 4 tuners through the same angle to 0.37 degrees – corresponds to 1m

– Concern- does rotating one at a time introduce some magnetic hysteresis effects?

• Only measuring X co-ord with a stretched wire system– not the highest resolution linear stages– measuring set-up is not thermally stablilized– thermal noise is significant (signals are very small)– precision of each measurement is 3-4 microns

• Nevertheless we’ve measured the X center– at various tuner rod angles, corresponding to different G.dl


Status of permanent “wedge” magnet measurements at SLAC, Jan 2001,pg 2/2

• X magnetic center observed to shift by up to 37m when strength is changed by rotating tuner rods. The larger the rotation the larger the x, 114 20% strength change 37um

• Several things could be causing these shifts, so not a final measurement, e.g. whole magnet moves as exert much force to rotate rods; stretched wire set-up maybe temp sensitive; rod starting angle wrong.

• Improvements being made to improve precision:– highest res linear stages about to be refurbished by Newport Corp– thermal noise being reduced; thermal stability to be improved– modify fitting routine

• From electromagnet measurements we know rotating coil’s precision in x/y is 0.02-0.2 m and is very stable so rotating coil’s length being extended so it can measure the permanent magnet prototypes

• Second wedge magnet being assembled with less stiff tuner rods


Sliding Shunt


Shunt Quad on SSW stand

•


Shunt Quad Test

• Gradient 101.7 Tesla\meter

• Maximum field 32.96 Tesla

• Minimum Field 28.50 Tesla

• 13.5% change

• Center Shift ~ 15 microns

• From Max field to Min field

• New design in works improve sliding bearings


Rotational quad

Permanent magnets


Rotating Quad

• Parts are in the shop

• Expect to have a magnet by March


Issues to test

• Center Stability

• Strength

• Repeatability in Tuning

• Speed of Gradient Change

• Radiation Hardness


Conclusions

• There are three prototype permanent magnet quads

• Two more on their way

• Two test stands SLAC and FNAL capable of doing measurements

• Both SLAC and Fermilab agree to better than 1 part in 10,000 on strength

• Will start rigorous test of stability

• Will chose “best” model this year

nlc - the next linear collider project nlc january video conference status of permanent quadrupoles...

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