First Electrons at the Fermilab superconducting test accelerator Elvin Harms Asian Linear Collider Workshop 2015, Tsukuba 24 April 2015

Introduction/Outline Overview of facility Recent Accomplishments –Electrons through Injector –preliminary results –CM-2 Future Prospects Summary 4/24/15E. Harms | First electrons at the Fermilab SRF test accelerator2

Overview of Facility Photoinjector Gun –Normal conducting 1-1/2 cell Laser –infrared > green > ultraviolet Capture Cavities –1 installed –another being prepped for installation User line including chicane 22.5° down bend to Beam Absorber 4/24/15E. Harms | First electrons at the Fermilab SRF test accelerator3

Recent Accomplishments – Electrons First accelerated electrons to beam absorber on 27 March –<2 days of tuning Regular operation since 4/24/15E. Harms | First electrons at the Fermilab SRF test accelerator4

Recent Accomplishments – Electrons Typical Operating Parameters –Laser spot size =  H = 235  m,  V = 187  m –pC/bunch = 250 typical, peak single bunch peak = 1 nC –# Bunches = –Gun voltage = 42 MV (4.5 MeV) –CC2 voltage = 15 MV/m –Transmission to beam absorber = 100% (22 meters) 4/24/15E. Harms | First electrons at the Fermilab SRF test accelerator5

Recent Accomplishments – Electrons Current Activities –commission Machine Protection System –center beam through quadrupoles –commission diagnostics BPM’s streak camera profile monitors –verify lattice/machine parameters 4/24/15E. Harms | First electrons at the Fermilab SRF test accelerator6 YAG screen image at end of line

Preliminary results – CC2 Transfer Function Measurement 4/24/15E. Harms | First electrons at the Fermilab SRF test accelerator7 Analysis in progress BPM’s before CC2 BPM’s after CC2

Preliminary results – Energy and Dispersion 4/24/15E. Harms | First electrons at the Fermilab SRF test accelerator8 Beam Energy [MeV] = 0.03 x (N:D122FF [Gauss]) x / sin(22.41Deg) = N:D122CE Beam centroid at end of line Beam width at end of line Fixed Angle No steering through quads E ~20 MeV

Preliminary results – Energy and Dispersion Cont. 4/24/15E. Harms | First electrons at the Fermilab SRF test accelerator9 D = mm

Preliminary results – Cathode QE Scan 4/24/15E. Harms | First electrons at the Fermilab SRF test accelerator10 1 nC/bunch QE ~2.5%

Preliminary results – CC2 Phase Scan – Ceramic Gap 4/24/15E. Harms | First electrons at the Fermilab SRF test accelerator11 Ceramic Gap is sensed with a self-calibrating 30 GHz  wave horn indication of off-crest bunch narrowing? more study needed CC2 phase intensity at ceramic gap  wave diode response CC2 crest

Preliminary results – CC2 Phase Scan with varied charge 4/24/15E. Harms | First electrons at the Fermilab SRF test accelerator12 CC2 +7° off-crest CC2 on-crest CC2 -7° off-crest Charge from Photoinjector Beam Centroid at beam absorber (after spectrometer) indication of charge-dependent energy variation charge-dependence varies with CC2 phase charge-dependent loss mechanism e.g. synchrotron light? more study needed

Recent Accomplishments – CM-2 CM-2 has achieved an average cavity gradient of 31.5 MV/m with all 8 cavities powered simultaneously 1.6 millisecond pulse width, 5 Hz repetition rate Lorentz Force Detuning Compensation (LFDC) on and ‘adapting’ LLRF operated in ‘closed loop’ Peak accelerating voltage = 252 MV Cavity 8 Warm coupler vacuum problem repaired in situ –required warm-up to room temperature Successful cool down and resumption of operation 4/24/15E. Harms | First electrons at the Fermilab SRF test accelerator13

Recent Accomplishments – CM-2 4/24/15E. Harms | First electrons at the Fermilab SRF test accelerator14 Snapshot of cavity gradients 31.5 MV/m CM2 Amplitude (MV/m, left) & Phase (right)

Future Prospects Increase intensity Commission chicane (compressed bunches) –coherent diffraction radiation –micro-bunch detection Single crystal channeling experiment Install CC1 – up to 55 MeV final energy Beam through cryomodule –tunnel extension –beam line –etc. 4/24/15E. Harms | First electrons at the Fermilab SRF test accelerator15

Summary ASTA is now operational at 20 MeV Commissioning activities in progress Increased energy after CC1 is installed: up to 55 MeV CM-2 met 31.5 MV/m specification Beam through cryomodule in /24/15E. Harms | First electrons at the Fermilab SRF test accelerator16 thanks to Fermilab IOTA/ASTA group, especially Dan Broemmelsiek and Chip Edstrom, for information and beam results

Thank You for your attention Questions? 4/24/15E. Harms | First electrons at the Fermilab SRF test accelerator17