June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 1 LCLS Magnet Damage Management Heinz-Dieter Nuhn, SLAC / LCLS June 19, 2008 Present Strategies for LCLS Beam Loss Monitoring Review of the Individual Magnet Irradiation Test T-493 Results of Damage Measurements Plans for follow-up Mini-Undulator Irradiation Test Present Strategies for LCLS Beam Loss Monitoring Review of the Individual Magnet Irradiation Test T-493 Results of Damage Measurements Plans for follow-up Mini-Undulator Irradiation Test

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 2 LCLS Beam Loss Monitors (BLMs) Strategies Radiation protection of the permanent magnet blocks is very important. Funds have been limited and efforts needed to be focused to minimize costs. A Physics Requirement Document, PRD exists, defining the minimum requirements for the Beam Loss Monitors. The damage estimates are based on published measurement results and a in-house simulations. Radiation protection of the permanent magnet blocks is very important. Funds have been limited and efforts needed to be focused to minimize costs. A Physics Requirement Document, PRD exists, defining the minimum requirements for the Beam Loss Monitors. The damage estimates are based on published measurement results and a in-house simulations.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 3 Estimated Radiation-Based Magnet Damage The loss of magnetization caused by a given amount of deposited radiation has been estimated by Alderman et al. [i] in [i] Their results imply that a 0.01% loss in magnetization occurs after exposure to a fast-neutron fluence of n/cm 2. A more recent report by Sasaki et al. [ii] challenges fast neutron fluence as damaging factor and, instead, proposes photons and electrons but does not provide a relation between integrated dose and damage.[ii] [i][i] J. Alderman, et. A., Radiation Induced Demagnetization of Nd-Fe-B Permanent Magnets, Advanced Photon Source Report LS-290 (2001) [ii][ii] S. Sasaki, et al, Radiation Damage to Advanced Photon Source Undulators, Proceedings PAC2005. The loss of magnetization caused by a given amount of deposited radiation has been estimated by Alderman et al. [i] in [i] Their results imply that a 0.01% loss in magnetization occurs after exposure to a fast-neutron fluence of n/cm 2. A more recent report by Sasaki et al. [ii] challenges fast neutron fluence as damaging factor and, instead, proposes photons and electrons but does not provide a relation between integrated dose and damage.[ii] [i][i] J. Alderman, et. A., Radiation Induced Demagnetization of Nd-Fe-B Permanent Magnets, Advanced Photon Source Report LS-290 (2001) [ii][ii] S. Sasaki, et al, Radiation Damage to Advanced Photon Source Undulators, Proceedings PAC2005.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 4 Estimate of Neutron Fluences from LCLS e - Beam The radiation deposited in the permanent magnets blocks of the LCLS undulator, when a single electron (e - ) strikes a 100-µm carbon foil upstream of the first undulator, has been simulated by A. Fasso [iii].[iii] The simulations predict a peak total dose of 1.0×10 -9 rad/e - including a neutron (n) fluence of 1.8×10 -4 n/cm 2 /e -, which translates into 1.8×10 5 n/cm 2 for each rad of absorbed energy. These numbers are based on peak damage results and should therefore be considered as worst case estimates. [iii][iii] A. Fasso, Dose Absorbed in LCLS Undulator Magnets, I. Effect of a 100 µm Diamond Profile Monitor, RP-05-05, May The radiation deposited in the permanent magnets blocks of the LCLS undulator, when a single electron (e - ) strikes a 100-µm carbon foil upstream of the first undulator, has been simulated by A. Fasso [iii].[iii] The simulations predict a peak total dose of 1.0×10 -9 rad/e - including a neutron (n) fluence of 1.8×10 -4 n/cm 2 /e -, which translates into 1.8×10 5 n/cm 2 for each rad of absorbed energy. These numbers are based on peak damage results and should therefore be considered as worst case estimates. [iii][iii] A. Fasso, Dose Absorbed in LCLS Undulator Magnets, I. Effect of a 100 µm Diamond Profile Monitor, RP-05-05, May 2005.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 5 Simulated Neutron Fluences for LCLS e - Beam on C Foil Simulated neutron fluences in the LCLS undulator magnets (upper jaw) from a single electron hitting a 100-µm-thick carbon foil upstream of the first undulator. Maximum Level is 1.8×10 -4 n/cm 2 /e - Simulated neutron fluences in the LCLS undulator magnets (upper jaw) from a single electron hitting a 100-µm-thick carbon foil upstream of the first undulator. Maximum Level is 1.8×10 -4 n/cm 2 /e -

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 6 Total Dose from LCLS e - Beam on C Foil Corresponding maximum deposited dose. Maximum Level is 1.0×10 -9 rad/e - Corresponding maximum deposited dose. Maximum Level is 1.0×10 -9 rad/e -

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 7 Radiation Limit Estimates Neutron Fluence for 0.01 % magnet damage from Alderman et al n/cm 2 Maximum neutron fluence in LCLS magnets from hit on 100 micron C foil from Fasso1.8×10 -4 n/cm 2 /e - Maximum total dose in LCLS magnets from hit on 100 micron C foil from Fasso1.0×10 -9 rad/e - Ratio of neutron fluence per total dose1.8×10 5 n/cm 2 /rad Maximum total dose in LCLS magnets for 0.01 % damage5.5×10 5 rad Nominal LCLS lifetime20years Number of seconds in 20 years6.3×10 8 s Maximum average permissible energy deposit per magnet0.88mrad/s Corresponding per pulse dose limit during 120 Hz operation7.3µrad/pulse ~ Hz; ~1 mrad/s

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 8 Neutral; K=3.4881;  x= 0.0 mm Undulator Roll-Away and K Adjustment Function First; K=3.5000;  x=-4.0 mmRoll-Out; K=0.0000;  x=+80.0 mm Horizontal Slide Pole Center Line Vacuum Chamber

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 9 Maximum Estimated Radiation Dose from BFW Operation Maximum neutron fluence in magnets of the last undulator due to BFW hit; based on Fasso simulations; scaled to Total Charge: 1 nC; Wire Material: C; Wire Diameter 40 µm; RMS Beam radius 37 µm; 1.5×10 5 n/cm 2 /pulse Corresponding radiation dose1rad/pulse Ratio of peak BFW dose to maximum average dose limit10 5 Radiation dose received by last undulator by 33 full x and y scans100rad Maximum number of full BFW scans to reach 20 % a maximum dose budget10 3 All Undulators Rolled-In Maximum neutron fluence in magnets of an undulator on same girder due to BFW hit; based on Fasso simulations; scaled to Total Charge: 1 nC; Wire Material: C; Wire Diameter 40 µm; RMS Beam radius 37 µm; 1.5×10 3 n/cm 2 /pulse Corresponding radiation dose10mrad/pulse Ratio of peak BFW dose to maximum average dose limit10 3 Radiation dose received by last undulator by 33 full x and y scans1rad Maximum number of full BFW scans to reach 20 % a maximum dose budget10 5 Undulators on DS Girders Rolled-Out (1/100) The small amount of scans expected, can be ignored for damage purposes; but might require MPS exception.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 10 Radiation Sources Possible reasons for generating elevated levels of radiation are Electron Beam Steering Errors Will be caught and will lead to beam abort. Unintentional Insertion of Material into Beam Path Will be caught and will lead to beam abort. Intentional Insertion of Material into Beam Path BFW operation Is expected to produce the highest levels. May only be allowable when all down-stream undulators are rolled-out and beam charge is reduced to minimum. Screen insertion May only be allowable when all undulators are rolled-out and beam charge is reduced to minimum. Background Radiation from Upstream Sources including Tune-Up Dump Expected to be sufficiently suppressed by PCMUON collimator. Beam Halo Expected to be sufficiently suppressed through upstream collimation system. May require halo detection system.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 11 General Requirements One BLM device will be mounted upstream of each Undulator Segment The BLM will provide a digital value proportional to the amount of energy deposited in the device for each electron bunch. The monitor shall be able to detect and measure (with a precision of better than 25%) radiation levels corresponding to magnet dose levels as low as 10 µrad/pulse [0.1 µGy/pulse] and up to the maximum expected level of 10 mrad/pulse [100 µGy/pulse]. The monitor needs to be designed to withstand the highest expected radiation levels of 1 rad/pulse without damage. The radiation level received from each individual electron bunch needs to be reported after the passage of that bunch to allow the MPS to trip the beam before the next bunch at 120 Hz. NOT FULLY REALIZED

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 12 Monitor Requirements Each BLM device will be able to measure the total amount of absorbed dose covering the full area in front of the undulator magnets. Each BLM device will be calibrated based on the radiation generated by the interaction of a well known beam with the BFW devices. The calibration geometry will be simulated using FLUKA and MARS to obtain the calibration factors, i.e., the ratio between the maximum estimated damage in a magnet and the voltage produced by each BLM device. NOT FULLY REALIZED

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 13 Beam Loss Monitor Area Coverage Main purpose of BLM is the protection of undulator magnet blocks. Less damage expected when segments are rolled-out. One BLM will be positioned in front of each segment. Its active area will be able to cover the full horizontal width of the magnet blocks Two options for BLM x positions will be implemented to be activated by a local hardware switch: (a) The BLM will be moved with the segment to keep the active BLM area at a fixed relation to the magnet blocks. (b) The BLM will stay centered on the beam axis to allow radiation level estimates in roll-out position. Main purpose of BLM is the protection of undulator magnet blocks. Less damage expected when segments are rolled-out. One BLM will be positioned in front of each segment. Its active area will be able to cover the full horizontal width of the magnet blocks Two options for BLM x positions will be implemented to be activated by a local hardware switch: (a) The BLM will be moved with the segment to keep the active BLM area at a fixed relation to the magnet blocks. (b) The BLM will stay centered on the beam axis to allow radiation level estimates in roll-out position. NOT FULLY REALIZED

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 14 BLM Purpose The BLM will be used for two purposes A: Inhibit bunches following an “above-threshold” radiation event. B: Keep track of the accumulated exposure of the magnets in each undulator. Purpose A is of highest priority. It will be integrated into the Machine Protection System (MPS) and requires only limited dynamic range from the detectors. Purpose B is desirable for understanding long-term magnet damage in combination with the undulator exchange program but requires a large dynamic range for the radiation detectors (order 10 6 ) and much more sophisticated diagnostics hard and software. The BLM will be used for two purposes A: Inhibit bunches following an “above-threshold” radiation event. B: Keep track of the accumulated exposure of the magnets in each undulator. Purpose A is of highest priority. It will be integrated into the Machine Protection System (MPS) and requires only limited dynamic range from the detectors. Purpose B is desirable for understanding long-term magnet damage in combination with the undulator exchange program but requires a large dynamic range for the radiation detectors (order 10 6 ) and much more sophisticated diagnostics hard and software.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 15 ANL Beam Loss Monitor Design Courtesy of W. Berg, ANL Rendering of Detector BLM Mounted on BFW in Front of Undulator Segment Beam A total of 5 BLM devices will be installed.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 16 Plan View of Short Drift Beam Loss Monitor Undulators Segments Quadrupole BPM BFW Beam Direction

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 17 Additional Loss Monitors Other Radiation Monitoring Devices Dosimeters Located at each undulator. Routinely replaced and evaluated. Segmented Long Ion Chambers Investigated (Quartz)-Fibers Investigated Non-Radiative Loss Detectors Pair of Charge Monitors (Toroids) One upstream and one downstream of the undulator line Used in comparator arrangement to detect losses of a few percent Electron Beam Position Monitors (BPMs) Continuously calculate trajectory and detect out-of-range situations Quadrupole Positions and Corrector Power Supply Readbacks Use deviation from setpoints Estimate accumulated kicks to backup calculations based on BPMs.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 18 LCLS Undulator Irradiation Experiment (T-493) The LCLS electron beam is stopped in a copper dump, and 9 samples of magnet material are positioned at different distances from the dump. The layout to achieve a range of doses is calculated using FLUKA. The radiation absorbed will be measured by dosimeters. Magnetization will be measured before and after exposure. The integrated beam current will be needed to be recorded to 10%. The LCLS electron beam is stopped in a copper dump, and 9 samples of magnet material are positioned at different distances from the dump. The layout to achieve a range of doses is calculated using FLUKA. The radiation absorbed will be measured by dosimeters. Magnetization will be measured before and after exposure. The integrated beam current will be needed to be recorded to 10%.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 19 Linac Coherent Light Source Near Hall Far Hall SLAC LINAC Undulator Tunnel Injector Endstation A T-493

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 20 T-493 Components installed ESA Beamline with copper cylinder and magnet blocks. Copper target for 13.7 GeV e - Beam. Diameter: 4 inches Length: 10 inches Dosimeters positioned at in the vicinity of each block. [See presentation by Johannes Bauer] ESA Beamline with copper cylinder and magnet blocks. Copper target for 13.7 GeV e - Beam. Diameter: 4 inches Length: 10 inches Dosimeters positioned at in the vicinity of each block. [See presentation by Johannes Bauer] Photo courtesy of J. Bauer BEAM

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 21 Magnet Block Assembly Straight-ahead mounting fixture on work bench with four magnet blocks (viewed in the direction of the beam.)

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 22 Mounted Magnet Block Next to Heat Shield Magnet block mounted next to heat shield. Mounting fixture with magnet for first forward position with heat shield.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 23 ANL Delivery of 12 LCLS Undulator Magnet Blocks Photo courtesy of S. Anderson Material: Ne 2 Fe 14 B Block Thickness: 9 mm Block Height: 56.5 mm Block Width: 66 mm Material Density: 7.4 g/cm 3 Block Volume:33.6 cm 3 Block Mass: g Curie Point: 310 °C Material: Ne 2 Fe 14 B Block Thickness: 9 mm Block Height: 56.5 mm Block Width: 66 mm Material Density: 7.4 g/cm 3 Block Volume:33.6 cm 3 Block Mass: g Curie Point: 310 °C

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 24 Pre-Irradiation Magnetic Moment Measurements The table shows the results of the measurement of magnetic moments for one of the magnet blocks (Serial No ) as an example. The Magnetic Moments are measured with a Helmholtz-Coil. All magnetic measurements have been carried out by Scott Anderson. The table shows the results of the measurement of magnetic moments for one of the magnet blocks (Serial No ) as an example. The Magnetic Moments are measured with a Helmholtz-Coil. All magnetic measurements have been carried out by Scott Anderson.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 25 Magnet Block Assembly (Top View) Beam Direction Copper Cylinder Magnet Blocks r z Top View Heat Shield 4 Magnet blocks in forward direction 5 Magnet blocks in transverse direction 3 Magnet blocks kept for reference M4 M3M2 M1 M8 M5 M6 M7 M9

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 26 Magnet Block Assembly (View in Beam Directions) y r View in Beam Direction Heat Shield Copper Cylinder Magnet Blocks M1-M4 M7M8 M6 M9 M5

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 27 Experiment T-493 Shift Records Magnet Irradiation Experiment T-493 ran for 38 shifts from 7/27-8/09/2007 Magnet Irradiation Experiment T-493 ran for 38 shifts from 7/27-8/09/2007

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 28 Delivered Power Delivered power levels alternated between about 125 W during Day and Swing Shifts and 185 W during Owl Shifts. During Day and Swing Shifts the experiment ran parasitically with LCLS commissioning. Delivered power levels alternated between about 125 W during Day and Swing Shifts and 185 W during Owl Shifts. During Day and Swing Shifts the experiment ran parasitically with LCLS commissioning.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 29 Tunnel Temperature Profile The temperature in the ESA tunnel stayed between °C during the entire 12-day data collection period. The plot shows diurnal cycle fluctuations. The temperature in the ESA tunnel stayed between °C during the entire 12-day data collection period. The plot shows diurnal cycle fluctuations.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 30 Magnetic Moment Evaluations: Results Summary Shown are parameters for the 9 irradiated magnets and the Cu target the estimated neutron fluence and dose levels peak power levels temperature estimates The last two columns contain the results of the magnets’ demagnetization measurements. Shown are parameters for the 9 irradiated magnets and the Cu target the estimated neutron fluence and dose levels peak power levels temperature estimates The last two columns contain the results of the magnets’ demagnetization measurements.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 31 Detailed FLUKA model of the experiment 13.7 GeV electron beam impinging on the copper dump Computation of total dose, electromagnetic dose, neutron energy spectra Quantity scored using a binning identical to the one used for the mapping of the magnetization loss Beam M3 M2 M5 M4 M6 M7 M1 M8 M9 Courtesy of J. Vollaire, SLAC

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 32 Damage Gradients M3 M1 M2 M4 M3 M1 M2 M4 Threshold Estimates for 0.01 % Damage SourceDeposited EnergyDose Neutron Fluence T kJ0.70 kGy0.070 MRad0.64×10 11 n/cm 2 TTF-2 (Lars Fröhlich)0.5 kGy0.05 MRad Previous Estimate1.4 kJ5.5 kGy0.55 MRad1×10 11 n/cm 2 FLUKA Simulations by J. Vollaire, SLAC

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 33 Additional Evaluation: Field Map Measurements Grid Size: 26 x 31 Points = 806 Points; Point Spacing: 2 mm; Method: Hall Probe Reference Magnet SN16673

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 34 Field Map Measurements for M1 Absolute Magnetic Field Amplitudes [T] Reference Magnet Fields subtracted [T]

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 35 Field Map Measurements for M2 Absolute Magnetic Field Amplitudes [T] Reference Magnet Fields subtracted [T]

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 36 Field Map Measurements for M3 Absolute Magnetic Field Amplitudes [T] Reference Magnet Fields subtracted [T]

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 37 Field Map Measurements for M5 Absolute Magnetic Field Amplitudes [T] Reference Magnet Fields subtracted [T]

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 38 Example of Dose Mapping for the Four Downstream Samples Courtesy of J. Vollaire, SLAC Fluence [cm -2 ]Total Dose [J cm -3 ]

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 39 Dose Profile versus Magnetization Loss Profile Courtesy of J. Vollaire, SLAC

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 40 Next Experiments T-493 was a measurement of the demagnetization of stand-alone magnets with no significant demagnetizing fields present. Inside an undulator, the magnet blocks will be tightly packaged next to one another and magnet blocks might experience the magnetic fields of the neighboring magnets. This scenario will be covered by the “Mini – Undulator Irradiation Test”. Ben Poling, SLAC, has designed and built a Mini-Undulator from spare LCLS Undulator magnet and pole pieces. A second Mini-Undulator (for reference) will be built before the first irradiation run. The magnetization of individual magnet pieces as well as the on-axis magnetic field of the assembled Mini-Undulators will be measured before and after the irradiation processes. Irradiation will be done similar to T-493: A radiation field will be generated by the LCLS electron beam hitting a copper target in ESA. This time, irradiation will be done in phases.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 41 Courtesy of B. Poling, SLAC Mini-Undulator Design by Ben Poling

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 42 Mini-Undulator Design by Ben Poling Courtesy of B. Poling, SLAC Made from spare LCLS undulator magnet blocks (2 x 2 x 3) and pole pieces (2 x 2 x 5). Total number of periods: 3. Gap height and period length identical to LCLS undulator. Made from spare LCLS undulator magnet blocks (2 x 2 x 3) and pole pieces (2 x 2 x 5). Total number of periods: 3. Gap height and period length identical to LCLS undulator.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 43 Schedule for Test Sequence Friday, May 16, :00- Monday, May 19, :00First irradiation run. Thursday, June 19, 2008Irradiation Collaboration Meeting Friday, June 27, :00- Monday, June 30, :00Second irradiation run. Friday, July 11, :00- Monday, July 14, :00Third irradiation run. Friday, August 1, :00- Monday, August 4, :00Fourth irradiation run. MINI-UND RUN 1 MINI-UND RUN 2 MINI-UND RUN 4 MINI-UND RUN 3 CANCELED

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 44 Summary The plan for monitoring and protecting the LCLS undulators from radiation was presented. Irradiation test at SLAC have been carried out in August 2007: Nine of the spare Nd 2 Fe 14 B permanent magnet pieces for the LCLS undulators have been exposed to radiation fields of various intensities under conditions that can be precisely calculated by FLUKA simulations. The total exposure time was 12.5 days during which a copper target was hit by the 13.7 GeV LCLS electron beam. The total energy of the 36.8x10 15 electrons that hit the target was 80 MJ. After a cool-down period, the magnetization levels of the magnets have been measured and compared with the pre-irradiation values. The difference is being compared to the (FLUKA) estimated radiation levels received. In addition, Mini-Undulators (3 periods, each) have been prepared for testing. The magnetic moments of each of the magnets as well as the on-axis magnetic fields after assembly will be measured and recorded. The plan is to irradiate one of them in up to four periods. The present plan to do the irradiation before the August shutdown will probably not work out.

June 19, 2008 Heinz-Dieter Nuhn, SLAC / LCLS LCLS Magnet Damage Management 45 End of Presentation