HOM Experiences at the SNS SCL SPL HOM Workshop CERN June 26, 2009 Sang-ho Kim SNS SCL Area Manager SNS/ORNL 2Managed by UT-Battelle for the U.S. Department of Energy SPL HOM Workshop at CERN, June 25-26, 2009 Outline SNS Intro HOM concerns in SNS SRF cavity Reminder of past histories HOM coupler issue Re-evaluation HOM frequency statistics SNS beam Beam induced signal Summary 3Managed by UT-Battelle for the U.S. Department of Energy SPL HOM Workshop at CERN, June 25-26, 2009 SNS Accelerator Complex 945 ns 1 ms macropulse Current mini-pulse Current 1ms Front-End: Produce a 1-msec long, chopped, H- beam 1 GeV LINAC Accumulator Ring: Compress 1 msec long pulse to 700 nsec Chopper system makes gaps Ion Source 2.5 MeV1000 MeV87 MeV CCL SRF, = 0.61 SRF, = MeV387 MeV DTL RFQ Accumulator Ring RTBT Target HEBT InjectionExtraction RF Collimators Liquid Hg Target 4Managed by UT-Battelle for the U.S. Department of Energy SPL HOM Workshop at CERN, June 25-26, 2009 SNS SRF cavity Fundamental Power Coupler HOM Coupler HOMB HOM Coupler HOMA Field Probe Tuner Helium Vessel Major Specifications: E a =15.9 MV/m at =0.81 E a =10.2 MV/m at =0.61 & Q o > 5E9 at 2.1 K 5Managed by UT-Battelle for the U.S. Department of Energy SPL HOM Workshop at CERN, June 25-26, 2009 Designed to operate at 2.1 K (superfluid helium) Fundamental power couplers Return end can Helium vessels Space frame Supply end can SNS Cryomodule 11*Medium beta 12*High beta 81 cavities 6Managed by UT-Battelle for the U.S. Department of Energy SPL HOM Workshop at CERN, June 25-26, 2009 Beam power history Summer 2007 Winter 2007 Summer 2008 Spring 2007 Fall 2006 Winter 2008 Summer 2009 7Managed by UT-Battelle for the U.S. Department of Energy SPL HOM Workshop at CERN, June 25-26, 2009 ParametersDesign Individually achieved Highest production beam Beam Energy (GeV) Peak Beam current (mA) Average Beam Current (mA)2624 Beam Pulse Length ( s) Repetition Rate (Hz)60 Beam Power on Target (kW) Linac Beam Duty Factor (%) Beam intensity on Target (protons per pulse)1.5 x x x SCL Cavities in Service8180 Major Parameters achieved vs. designed 8Managed by UT-Battelle for the U.S. Department of Energy SPL HOM Workshop at CERN, June 25-26, 2009 SCL status SCL is providing a very reliable operation for neutron production following SNS power ramp-up Down time < 5 min/day (