SuperConducting Undulator (SCU) R&D Motivation and Status P. Emma For the SCU R&D collaboration: ANL, LBNL, SLAC June 27, 2014

Kicking the Can Down the Road (SCU’s)… Proposed by E. Gluskin in 1999 for LCLS-I  “not ready for SCU” (15 yrs ago) Re-baseline LCLS-II HXR undulator and greatly improve performance (to 8 keV)? SCU’s operating in ANKA (2005) & APS (2013) right now Need to be developed now for future FELs (and LCLS-II ?)

Superconducting Undulator Motivation Using an SCU for the LCLS-II HXR undulator… Allows full LCLS-II performance to 5 keV+ (SASE & self- seeded) and with 50 m less undulator (or more taper) More aggressive design may allow 8 keV in LCLS-II at 1 MHz Has orders of mag. less sensitivity to radiation dose (1 MHz!) Is much less sensitive to e  emittance (new high-rate gun) Produces very low pressure in a small vacuum chamber (gas scattering at 1 MHz) Enhances LCLS-I FEL power, whereas a new PMU degrades it Provides a better base for LCLS-II upgrades long into the future (e.g., 10 keV at 4.8 GeV)

SCU R&D Plan ANL… Build 2-m test cryostat (based on existing APS design) Build & test 1.5-m long NbTi prototype planar undulator ( u  21 mm) LBNL… Build & test 1.5-m long Nb 3 Sn prototype planar undulator ( u  19 mm) Measure, correct, and tune both undulators (+ short test cryostat at LBNL) Both Labs… Develop field measurement and field correction techniques Demonstrate predicted field, field quality, end-field corrections, field measurement and tuning, cold mass fiducialization, and integration of cold mass into cryostat Develop conceptual design for 140-m SCU for LCLS-II? Goal: Within 18 months (July 2015) deliver 2 fully functional, 1.5-m long, SC prototype undulators which meet LCLS-II specifications White paper on possible LCLS-II SCU (by Jan. 2015?)

Undulator Parameters ANL LNBL Based on at least eV in LCLS-II at 4 GeV

Brief Status Requirements laid out for each undulator Magnet Design Review held June 6 (2 magnets & 1 cryostat) Designs are quite advanced (LBNL action items on cryo connections and 2 nd support frame) Correctors and end-field terminations are designed Cryostat procurement in process (both labs) ANL cryostat assembly starts in January 2015 (ahead of schedule) Will hold “next phase” meeting July 8 to discuss conceptual design of 140-m system (cold breaks, alignment, cryo, etc)

SCU’s Provide Real Performance Enhancement SCU (Nb 3 Sn) SCU (NbTi) PMU (NdFeB) PMU (in-vac) gap = 7.5 mm (5.7 mm for in-vac  same stay-clear) SCU  much higher field for given period, u, and gap LCLS-II PMU: u = 26 mm B pk = 1.0 T gap = 7.2 mm

Undulator Length vs. e  Energy for LCLS-II HXR PM In-Vac NbTi Nb 3 Sn u = 27.5 mm, 24.8 mm, 20.3 mm, 18.7 mm (4 GeV) keV Self-Seeded (SS) u = 16.3 mm u = 20.3 mm u = 18.7 mm g = 7.5 mm  = 0.45  m I pk = 1 kA  E = 500 keV  = 15 m g = 7.5 mm  = 0.45  m I pk = 1 kA  E = 500 keV  = 15 m Period varies with energy to maintain lower-limit tuning range (1.2 keV) 65 m 5.7 mm stay-clear in all cases

PMU (g m = 7.2 mm) PMU (g m = 6.3 mm) NbTi Nb 3 Sn Possible HXU for LCLS-II (toward 8 keV SASE) Nb 3 Sn (E = 4.2 GeV) SASE only E = 4.0 GeV  = 0.40  m I pk = 1 kA  E = 500 keV  = 16 m 20% L u margin 3.4-m seg’s 1.0-m breaks 1 und. missing 1.5 keV low-lim. SASE only E = 4.0 GeV  = 0.40  m I pk = 1 kA  E = 500 keV  = 16 m 20% L u margin 3.4-m seg’s 1.0-m breaks 1 und. missing 1.5 keV low-lim. * 4.0-mm vacuum chamber stay-clear in all cases (except PMU=5) 8 keV u = 24.4 mm, 25.6 mm, 18.4 mm, 16.8 mm (op. point) 145-m limit g m = 6.3 mm* Cu linac still produces 1-25 keV with slightly better power ~7 keV HXRSS limit

Upgrading to 10 keV (4.8 GeV) 10 keV 145-m limit Nb 3 Sn (E = 4.2 GeV) Nb 3 Sn (E=4.8 GeV)  = 0.40  m I pk = 1 kA  E = 500 keV  = 16 m 20% L u margin 3.4-m seg’s 1.0-m breaks SASE only 1 und. missing  = 0.40  m I pk = 1 kA  E = 500 keV  = 16 m 20% L u margin 3.4-m seg’s 1.0-m breaks SASE only 1 und. missing g m = 6.3 mm*  2.1 keV lower limit at 4.8 GeV  PMU at 26-mm per. provides 6.5 keV SASE at 4.8 GeV 8.3 keV HXRSS limit

Resistive-Wall Wake Amplified by Smaller Chamber (may reduce photons by factor < 2, but still 8 keV with ~1 GW)  full chamber gap = 5 mm Aluminum Rectangular 100-m long 8-fs relax-time  c = 3.6E7  -m    full chamber gap = 4 mm 100 pC

“TW-FEL” with SCU’s at SLAC (LCLS-II)? Z. Huang “ ” - 20 mJ in 20 fs in 2020

Magnetic Gap Calculation (April 15, 2014) Y. Ivanyushenkov

Undulator Tolerances (Nb 3 Sn & NbTi, 4 GeV & 15 GeV) H.-D. Nuhn

LBNL Design (Nb 3 Sn)

LBNL - Termination Coils Odd number of poles (8x7 = 56) Ideal end design used for main coil: 1/8, 1/2, 7/8

LNBL - Undulator Assembly Components

ANL - New Coil Winding Scheme Short Test Cores

ANL - End-Coil Winding Scheme

ANL - Measured B y and 1 st Field Integrals at 500 A Plot shows effects of compensation coils operated over full 100-A range (SCU0). Compensation coils connected in series and energized to: 0, 51, and 100 A. First field integrals are calculated from measured B-field data. Tolerance: 40 G-cm

ANL - 2-m Cryostat (used for both magnets)

ANL – He Tank for SCU0 Assembly Cold-mass support frame might be added to LNBL magnet also (12k$)?

Schedule (rolled up) magnet testing March 2015 magnet testing March 2015 complete July 2015 complete July 2015 magnet review June 2014 magnet review June 2014 start

Budget (FY14 - FY15) with new BES Funds SLAC funds paid to ANL so far:636 k$ (of 1920) SLAC funds paid to LBNL so far:223 k$ (of 526) BES funds paid to ANL so far:200 k$ (of 400)

Issues for “Next Phase” – Meet July 8 How to join two 1.5-m long sections with minimal space, controlled field integrals, proper phasing? Warm breaks or cold (quads, BPMs, phase shifters, steering coils)? 4K Helium transport, cryo power, and distribution? Absolute vertical alignment of undulator with tight (0.05-mm rms at 25 keV) tolerances and cryostat shell? Add alignment quadrupoles to both ends for beam- based alignment at both ends (as at SwissFEL)? Vertical trajectory corrections? (hor. field integrals) Conceptual SCU system design document by Jan. 2015?

LNBL - Summary One master power supply controls undulator field and three slave supplies provide end corrections. Basic mechanical design completed. – Single piece magnet mandrel – End joint assembly – Mechanical structure Reaction and impregnation tooling must be designed but processes are well understood Integration with ANL cryostat: – Have maintained same interfaces – Need to finalize the LHe cooling interface – Add cold-mass support frame to LBNL magnet?

ANL - Summary Magnet structure design and drawings are complete. Design is based on previous SCU0 and SCU1 magnets. New coil winding scheme should reduce skew quad. End-coil compensation same as proven SCU0 design. Two short magnetic structures have been manufactured and cold tested. SCU electrical connection scheme similar to SCU0, with improvements related to heat transfer. Procurement of 1.5-m magnet cores begins in August.