LSWG day, Sept. 2, 2014, B. Auchmann for the BLMTWG Collaboration of many teams: OP, RF, BI, Collimation, LIBD, FLUKA, etc. T. Baer, M. Bednarek, G. Bellodi, C. Bracco, R. Bruce, F. Cerutti, V. Chetvertkova, B. Dehning, P. P. Granieri, W. Hofle, E. B. Holzer, A. Lechner, E. Nebot Del Busto, A.Priebe, S. Redaelli, B. Salvachua, M. Sapinski, R. Schmidt, N. Shetty, E. Skordis, B.M. Solfaroli, D. Valuch, A. Verweij, J. Wenninger, D. Wollmann, M. Zerlauth

Quench Test Analysis What is the energy deposition in the coil at the moment of quench? Particle Shower FCBM: loss rate QPS: moment of quench Particle tracking: spatial distribution BLM signals Validation Input Analysis Electro-Thermal Estimate (MQED) BLM: normalized time distribution P. shower: norm. space distribution Quench test QPS: moment of quench Subscale experiments Quench Level Upper bound or estimate Lower bound Particle Tracking Settings: bump amplitude etc. Beam parameter measurements: ε, Q, etc. BLM normalized time distribution BPM signals

Why quench tests? To obtain binary quench/no-quench data for realistic beam loss scenarios, e.g., collimation (see Stefano’s talk), and single-turn losses on collimators (see Jan’s talk). To validate electro-thermal and particle-shower models used to set BLM thresholds, used to define requirements for upgrades. To understand beam loss scenarios relevant for BLM threshold

Single-Turn Losses (LIBD) 2011 MD2: Quench tests (QT) on Q4/TCSG and Q6/TCLIB at 450 GeV. No quenches occurred for varying collimator settings, bunch intensities, and orbit bump. BLM Callibration studies performed. Documentation: CERN-ATS-Note MD, W. Bartmann, et al., Quench Margin at Injection. C. Bracco, et al., Experiments on the Margin of Beam Induced Quenches for LHC Superconducting Quadrupole Magnet in the LHC, IPAC End-of-Run QT Campaign: Q6/TCLIB QT, 450 GeV bunches, variable magnet currents. Q6 magnet was quenched. No FLUKA validation with BLM data due to saturation. Moderate consistency. Documentation: C. Bracco, et al. Test and Simulation Results for Quenches Induced by Fast Losses on a LHC Quadrupole, IPAC Run 2 tests: Q4/TCSG test (see LIBD talk). Improve diagnostics by LICs?

UFO Time-Scale Losses 2010: Wire-scanner quench test on D4 magnet D4 K) quenched. Uncertainties due to timing and loss maximum in coil ends End-of-Run QT Campaign: ADT quench test MQ quenched. Large uncertainty on moment of quench. Large uncertainties in electro-thermal model. Best approximation of UFO-type losses in 1.9 K magnets.

UFO Time-Scale Losses 2013 End-of-Run QT Campaign: ADT quench test Preparatory MDs: 2012 MD 1/2/3, 2013 test Documentation CERN-ATS-Note MD, A. Priebe, et al., ADT fast losses MD M. Sapinski, et al., Generation of Controlled Losses in Milisecond Timescale with Transverse Damper in LHC, IPAC V. Chetvertkova, et al., MadX Tracking Simulations to Determine the Beam loss Distributions for the LHC Quench Tests with ADT Excitation, IPAC N. V. Shetty, et al., Energy Deposition and Quench Level Calculations for Millisecond and Steady-state Quench Tests of LHC Arc Quadrupoles at 4 TeV, IPAC2014. C. Bracco, et al. Test and Simulation Results for Quenches Induced by Fast Losses on a LHC Quadrupole, IPAC M. Sapinski, et al., Beam-induced Quench Tests of LHC Magnets, IPAC PRSTAB paper to be submitted in autumn A. Priebe, CERN-THESIS Run 2 tests: Repeat ADT quench test with improvements: better instrumentation (oscilloscope), complete set of beam-parameter measurements just before the test, good understanding of ADT settings, even faster losses. In parallel we aim at improving the electro-thermal model; see BIQ workshop, Sept , (

UFO Time-Scale Losses Run 2 tests continued: Study losses induced by fast current-change in RD1.L/R1 (B. Dehning): Based on CERN-THESIS , Andres Gomez Alonso Retreat collimators and create orbit bump in MQ. Lose pilot bunch within ~10 turns due to orbit distortion. Detailed study needed.

Steady-State Losses 2010 Dynamic orbit bump quench tests at injection and 3.5 TeV Quenches in MQ at 450 GeV and 3.5 TeV. Analysis results will be used to se low-energy arc and DS thresholds. Documentation: A. Priebe, et al., Beam-induced Quench Test of a LHC Main Quadrupole, IPAC A. Priebe, et al., Investigation of Quench Limits of the LHC Superconducting Magnets, IEEE Trans. On Appl. SC, Vol 23, No 3, June A. Priebe, CERN-THESIS PRSTAB paper to be submitted in autumn Collimation quench tests (see Collimation talk) No quenches occurred! 2013 End-of-Run QT Campaign ADT quench test MQ quenched after 20 s of steady losses. FLUKA/BLM discrepancy. Modest (30 µm) step in surface roughness could produce a better fit to BLM data. No full validation of electro-thermal model.

Steady-State Losses 2013 End-of-Run QT Campaign ADT quench test continued. Documentation: V. Chetvertkova, et al., MadX Tracking Simulations to Determine the Beam loss Distributions for the LHC Quench Tests with ADT Excitation, IPAC N. V. Shetty, et al., Energy Deposition and Quench Level Calculations for Millisecond and Steady-state Quench Tests of LHC Arc Quadrupoles at 4 TeV, IPAC2014. M. Sapinski, et al., Beam-induced Quench Tests of LHC Magnets, IPAC PRSTAB paper to be submitted in autumn A. Priebe, CERN-THESIS Run 2 tests: Repeat ADT quench test with improvements: complete set of beam-parameter measurements just before the test, good understanding of ADT settings, in a different aperture or magnet. In parallel we aim at improving the electro-thermal model; see BIQ workshop, Sept , (

Summary Series of successful quench tests help to improve and validate the electro-thermal model, set BLM thresholds for Run 2. Additional tests are required to validate the steady-state quench levels, Improve knowledge on UFO time-scale losses.

Wire Scanner Installation of a wire scanner to produce losses in Q7 or further downstream. Affected magnets at 1.9 K (in contrast to installed WS). Considerable cost (B. Dehning rough estimate 200 kCHF). Installation during long stop for vacuum issues. Requires pre-study: Losses in magnet ends lead to large error margins in the analysis. See if losses can be generated in the longitudinal center of the magnet. Could provide “UFO factory” – if needed.