NLC - The Next Linear Collider Project James T Volk May 2002 Report to MAC on Magnets James T Volk Fermilab May 10, 2002

NLC - The Next Linear Collider Project Participants SLAC Seung Rhee, Cherrill Spencer, Jim Spencer SLAC Magnetic Measurement Group Scott Anderson, Zack Wolf Fermilab Magnetic Measurement Joe DiMarco James T Volk May 2002 LBNL Jose Alonso, Jin-Young Jung

NLC - The Next Linear Collider Project Recommendations from Oct ‘01 MAC Implement proposed upgrade of stability measurement systems Perform estimate on radiation damage tolerances allowed by NLC spec for each permanent magnet design Consider reducing the number of alternative designs Some effort should be devoted to determining if vibrations from LCW can be maintained with in specifications When a PM design meets NLC specs has been identified its cost for construction, installation and operation should be compared to an EM James T Volk May 2002

NLC - The Next Linear Collider Project Implement proposed upgrade of stability Measurement Systems Due to budget cap there is no money to upgrade the Fermilab system at this time SLAC has moved the rotating coil system to a small room from the high bay of the light assembly building. Improved temperature and humidity control Both SLAC and FNAL systems are adequate for current needs May 2002 James T Volk

NLC - The Next Linear Collider Project Perform estimate on radiation damage tolerances allowed by NLC spec for each PM design Still gathering information on expected radiation levels in Main LINAC and Damping Rings. Old Measurements from SLC and damping rings inconsistent due to assumptions and calculations So these data are little use to NLC. Have been doing measurements in SLC damping ring distinguish different types of particles Radiation levels do vary by orders of magnitudes and types depending on location. Need to get better models. Different types of radiation have different effects on Permanent Magnets. James T Volk May 2002

NLC - The Next Linear Collider Project Radiation Damage Issues SM Cobalt more resistant than ND-Iron –SM Cobalt more expensive –Has longer lived activation products –ND-Iron dependent on manufacturing process –And brick geometry Still need more investigation –Both literature –Do Computer modeling (FLUKA) –Network with other groups engaged in this type of work –And Experiments –Need to test actual magnets with real beams James T Volk May 2002

NLC - The Next Linear Collider Project Radiation-Induced Demagnetization (Japanese experience with 200 MeV protons) Material Type has large impact Red: N48 High Br (1.4T) Low Hc (1.15 MA/m) Blue:N32ZLower Br (1.14 T) Higher Hc (2.5 MA/m) Material Shape has large impact (All samples are discs 10 mm dia) Circle: thickness = 2 mm (Pc = 0.5) Triangle: thickness = 4 mm (Pc = 1.0) Square: thickness = 7 mm (Pc = 2.0) - Higher Permeance coefficient increases resistance (x 10) SmCo is much more resistant than NdFeB May 2002 James T Volk

NLC - The Next Linear Collider Project Have Radiation Test Dipole Design PM Material May 2002 James T Volk 2 inch gap

NLC - The Next Linear Collider Project Radiation Damage Testing First dipole is in FNAL shop expect to build 5-10 dipoles to test various aspects of magnets aging, different radiation fields, different manufacturers Have in hand 100 Hitachi ND-Iron magnets to start tests Have a space at FNAL LINAC to expose dipoles to 400 MeV neutrons and protons Need to find other sources of particles Looking for help from University groups –An Ideal project for a small group! James T Volk May 2002

NLC - The Next Linear Collider Project Aging Data From Dexter James T Volk May 2002

NLC - The Next Linear Collider Project Consider Reducing the Number of Alternative Designs Corner tuner has been eliminated Work on the sliding shunt and counter rotating quads has stopped due to budget cap New rod tuning mechanism for wedge tuner has been built center stability is encouraging Computer models of Wedge and Ring Quad are proceeding There is still time to explore models before the CDR is finalized in ‘04 James T Volk May 2002

NLC - The Next Linear Collider Project Wedge Quad Rod Turning Mechanism Tuning Rod May 2002 James T Volk Pin slides in slot turning rod

NLC - The Next Linear Collider Project Photo of the Wedge Quad on the SLAC measuring set-up. Wedge magnet, secured to V block Rotating coil read-out Tuning rods rotation mechanism. One rod only connected. Smaller gear wheel turned with wrench. Aluminum V block, secured to granite table Cooling fan for readout stand Heidenhain 0.5µm indicator May 2002 James T Volk

NLC - The Next Linear Collider Project FNAL SSW Measurements of Wedge Quad James T Volk May 2002

NLC - The Next Linear Collider Project SLAC Rotating Coil Data May 2002 James T Volk

NLC - The Next Linear Collider Project Finding Tuning Rod Minimum

NLC - The Next Linear Collider Project PM quad: centers measured repeatedly overnight on SLAC rotating coil set-up Even though room temp. which determines the Al block and magnet temp. is very constant (~0.1 °C), the Y center varies by > 1 µm and is ~ correlated with the Al block temp. X center varies <1 µm and is not correlated with Al Block temperature. James T Volk May 2002

NLC - The Next Linear Collider Project PM Wedge quad overnight in SLAC rotating coil setup measuring strength Strength of the PM quad measured repeatedly during ~18 hours. Various parts of apparatus and magnet have their temperatures measured at same time. Room has tightly controlled air temperature, nevertheless parts change temp by fractions of 1 °C. Quad is thermally compensated, else strength would change much more with temp. Slope of RH plot indicates integrated strength changes by T per °C James T Volk May 2002

NLC - The Next Linear Collider Project Studies Using Pandira James T Volk May 2002 f

NLC - The Next Linear Collider Project Further Tests Using rotating coil to find true minimum value for each rod Make new rods so we can attach potentiometers and get angle read out of rods Re-work wedge quad to allow for tuning of pole strength May 2002 James T Volk

NLC - The Next Linear Collider Project New data on the electromagnetic quad with improved magnetic measuring set-up. The SLAC rotating coil measuring set-up has been improved: a 5kW electric direct immersion water heater with an SCR controller has been put in the incoming cooling water circuit. Variations of ~ 4°C in LCW temp reduced to +/- 0.1 °C. Above plots show water temperatures during a 2.5 day run at 80 amps. James T Volk May 2002

NLC - The Next Linear Collider Project Electromagnet LINAC quad magnetic center measurements during 2.5 day run X and Y centers measured with improved rotating coil setup, each data point took 8 mins. X varies by < 1µm. Y has unexpected increase of ~3 µm over 10 hr period. Y values very sensitive to various apparatus temperatures, typically the magnet core steel. James T Volk May 2002

NLC - The Next Linear Collider Project Electromagnetic quad data from 2.5 day run at 80 amps constant Magnet steel core temp tracks incoming LCW temp. Y center correlates with magnet steel temp, but in this run does not explain 3 µm increase in Y. Have not found culprit, e.g. see no correlation with (very stable) magnet current. Suspect Y has NOT really moved but our set-up created that illusion. Will continue to understand/improve set-up. James T Volk May 2002

NLC - The Next Linear Collider Project Determining if Vibrations from LCW can be Maintained with in Specifications Andrei Seryi has plots more in his Saturday Talk James T Volk May 2002

NLC - The Next Linear Collider Project PM vs EM cost for Construction, Installation and Operation SLAC and Stanford engineering school working methodologies for cost estimation and reliability calculations. Still plenty of time between now ‘04 to explore and refine designs James T Volk May 2002

NLC - The Next Linear Collider Project Developing Methodologies to Estimate Overall Magnet Costs- including repair costs Use real failure data of magnets from similar accelerator to predict how often there will be failures of the magnets in the NLC. Estimate for a particular failure scenario how much it will cost to fix the failure– accounting for all aspects of the repair and the lost opportunity costs (for those failures happening during operations, when the accelerator is un-useable– have to ascribe an opportunity cost per hour). For real failure data: took all the magnet failures that brought down any beamline in SLAC during 5 year period. Using downtime reporting database we scrutinized every one of 75 failures as to its cause, type of magnet, length of time to detect and repair. Calculated number of SLAC magnets running during any period and how many hours they ran to calculate mean time between failures. Calculate availability values and extrapolate them to known number of NLC magnets running for 30 years. Estimate cost to fix all failures. James T Volk May 2002

NLC - The Next Linear Collider Project SLAC Downtime (Avg) SmallMediumLarge Magnet Size Number of Failures Small Non-Water Cooled MediumLarge Magnet Size Occurrence SLAC Downtime SmallMediumLarge Magnet Size Hours Magnet Failures at SLAC: Jan. 97 – Dec Downtime (hr) James T Volk May 2002

NLC - The Next Linear Collider Project Failure Frequency InsulationWater LeakWater Blockage Human Error ConnectorOther Failure Type Events InsulationWater LeakWater Blockage Human ErrorConnectorOther Failure Type Downtime (hr) SLAC Downtime by Failure Type James T Volk May 2002

NLC - The Next Linear Collider Project Water Cooled Magnets (Med & Large) Failures James T Volk May 2002

NLC - The Next Linear Collider Project Water Cooled Magnet Problems James T Volk May 2002

NLC - The Next Linear Collider Project LBNL & SLAC work on designing magnets (PMs and EMs) for the damping rings Main Damping Ring lattices have been published with detailed requirements on all magnets Have 2-D model of DR quadrupoles and transport line dipoles. The Nd Iron style magnets are of reasonable size Investigated the Nd Iron quads, with rotating rods to generate the +/-10% adjustability, in more detail to see if they could meet all the requirements. Jin-Young Jung (LBNL) used TOSCA to make a 3-D model of damping ring magnets Validated the new 3-D model of the Neo quad by simulating it as an infinitely long magnet similar to the PANDIRA code. Poletip fields predicted by the 2 codes agreed to within 0.2%, so TOSCA model good. James T Volk May 2002

NLC - The Next Linear Collider Project Results from 3-D model of PM DR quad DR magnets have to have a “C” shape – allow for the extra wide vacuum chamber to extend towards the outer edge of the ring and be –capable of accepting the high amounts of synchrotron radiation. The TOSCA 3-D model of a 2cm radius Neo quad was run with a 25 cm effective length. The poletip field was 10% less than in the 2-D PANDIRA model. –Decrease due to flux loss –End Plates do not help reduce this James T Volk May 2002

NLC - The Next Linear Collider Project TOSCA model of ¼ Neo quad with a steel end plate James T Volk May 2002

NLC - The Next Linear Collider Project NLC DR quad as an electromagnet:TOSCA model POISSON 2-D model was made of an electromagnet with same steel poletip shape as the pm. It satisfied the DR quad requirements. To allay concerns about the size of fringe field out of the end faces a 3-D TOSCA model was made. The coils were carefully modeled in 8 sections to look exactly like the real ones would.The model universe included air out to where the gradient dipole would be => fringe field < 2 gauss James T Volk May 2002

NLC - The Next Linear Collider Project NLC DR Gradient Dipole: TOSCA design. Studying end effects and fringe fields To allay concerns about the size of fringe field out of the end faces a 3-D TOSCA model was made. The coils were carefully modeled to look exactly like the real ones would.The model universe included air out to where the nearest quad would be => fringe field < 3 gauss TBD: calculate the multipole harmonics in 3D and check field quality is met. James T Volk May 2002

NLC - The Next Linear Collider Project Final Focus Magnet James T Volk May 2002

NLC - The Next Linear Collider Project Final Focus Magnet James T Volk May 2002

NLC - The Next Linear Collider Project Conclusions Slow but steady progress being made on LINAC quads We are quantifying the radiation fields in the Main Linac and Damping Rings First tests of radiation hardness are underway more ready to begin Working on Cost estimates and failure mode analysis Working on magnets for Damping Rings Looking at magnets for final focus May 2002 James T Volk