Status-Quo and Future Direction UFO Studies Status-Quo and Future Direction Presentation at the 37th BLM Thresholds Working Group Meeting L. Grob, B. Auchmann, J. Blomberg Ghini, R. Schmidt

The different approaches to the UFO problem UFO event tracking & database Statistical analysis Theoretical modelling Experimental studies

The different approaches to the UFO problem UFO event tracking & database Statistical analysis Theoretical modelling Experimental studies

UFO detection and foot prints Measured UFO signal Courtesy of T. Baer UFO characteristics: Localized beam losses Assymetric Gaussian Duration around 640 µs UFO Buster (2011)

UFO Buster working principle Software developed in Python (T. Bär, 2010-2013) Based on BLM integration times (RS1 40 µs, RS2 80 µs, RS 3 320 µs, RS 4 640 µs…) accessable via CCM → LHCOP → LHC control → Fixed Displays → BLM → UFO Buster (use only I/O tab) Algorithm based on the following assumption: Min. 2 BLMs within 40 m distance detect the beam loss signal Losses in RS 4 > 1∙10-4 Gy/s (noise level about 2∙10-5 Gy/s) Additional noise filters: RS2/RS1 > 0.55 RS3/RS1 > 0.30* *For MKI studies and 2011 data: RS1 > 1∙10-2 Gy/s RESULT: searchable UFO database

UFO Buster 2.0 (?) UFO Buster algorithm seems to register a lot of UFO-like losses, which always occur in the same components Q: How can we easily make sure, it‘s really UFOs? A: Look at elastic proton losses!

UFO losses in IP 7 to verify UFO event Idea: After UFO event the elastic scattered protons travel around the LHC At collimators (e.g. in IP 7) they are absorbed and seen as beam losses Proof of principle done for some UFOs with high RS4 losses: RS4IP7 BLM/RS4triggering BLM= 0.42 RS4IP7 BLM/RS4triggering BLM= 0.55 0.01 Gy/s 0.005 tUFO

Open questions regarding UFO detection Lowest detection limit for UFO event in IP7 Signal height in IP7, IP6 and IP3 wrt to triggering BLM Dependency on beta function Potential tool to simulate elastic losses and IP7 UFO signal Additional dBLM data with ns time resolution (the plot shows that the bunch structure can be fully resolved)

The different approaches to the UFO problem UFO event tracking & database Statistical analysis Theoretical modelling Experimental studies

UFO rate plots to quantify impact UFO Buster database can be analyzed via scripts (e.g. Mathematica or Python) Standardized plots of UFOs/hour (see above) UFO distribution along the ring wrt B1/B2 (see below, left), UFO events in standardized Arc FODO cell (see below, right) Beam 1 UFO rate along LHC courtesy of J. Ghini Beam 2 UFO rate along LHC courtesy of J. Ghini courtesy of J. Ghini

Current status & outlook G. Papotti looks into UFO rate comparison J. Blomberg Ghini, B. Auchmann and L. Grob use Mathematica-based scripts to produce the before-mentioned plots Hope: find new correlations (e.g. different UFO rates/severity in B1/B2, in different sectors or magnets) Idea: Migration to Python (faster, same language as UFO Buster) Development of analysis scripts, which can automatically produce some standard plots Regular creation frequency of those plots Maybe small software tool, which adds up to the UFO Buster (?)

The different approaches to the UFO problem UFO event tracking & database Statistical analysis Theoretical modelling Experimental studies

UFO Model simulates underlying physics Initiated by F. Zimmermann, revised and optimized by B. Auchmann and S. Rowan Analytical simulation of UFO event in Mathematica based on: UFO Buster UFO criteria, new BLM layout Physics input: beam parameters (σ, β, τ), transverse electrostatic E/B fields, mirror charges UFO differential equation (gravity, el. force), UFO Model output: reproduces UFO-shape charge and ionization rate Limitations: only based on gravity! Monte Carlo simulation of UFOs in Arc cells: UFO generator with: UFO location = [0, 2L], UFO path = ½ dbeam screen ,UFO radius = 0.5-25 µm Model output: 4 TeV simulations provided UFO size distribution for 6.5 TeV extrapolation, calculation of BLM responses and energy deposition (quench prediction) courtesy of B. Auchmann courtesy of S. Rowan (part of his upcoming thesis)

The different approaches to the UFO problem UFO event tracking & database Statistical analysis Theoretical modelling Experimental studies

UFO Busting anlysis of real LHC contaminants Course of action: Develop dust extraction procedure and tool Tests on stored beam screen parts, collection of reference samples from tunnel and assembly hall Extract dust from spare LHC magnets Analysis: Microscopic analysis (optical & SEM) Energy-dispersive X-ray diffraction (XEDS) or similar technique to reveal chemical composition Goal: Knowledge of UFO size distribution & material composition better understanding of release mechanism, UFO dynamics and hopefully removal

THANK YOU VERY MUCH FOR YOUR ATTENTION! I would like to thank the following people for their greatly appreciated support on that project: B. Auchmann, M. Barnes, P. Chiggiato, P. Cruikshank, A. T. Perez Fontenla, J. Blomberg Ghini, H. Kos, G. Iadarola, A. Lechner, S. Le Naour, G. Papotti, S. Rowan, N. Pietralla, R. Schmidt and the other co-workers of the technical department Selected literature: T. Bär, Very Fast Losses of the Circulating LHC Beam, their Mitigation and Machine Protection, CERN-THESIS-2013-233 B. Auchmann, „How to survive a UFO attack“ in 6th Evian workshop proceedings 2015 G. Papotti, „MACROPARTICLE-INDUCED LOSSES DURING 6.5 TEV LHC OPERATION “ in IPAC2016 proceedings S. Rowan, „INTERACTIONS BETWEEN MACROPARTICLES AND HIGH-ENERGY PROTON BEAMS“ in IPAC2015 proceedings This work is sponsored by the Wolfgang-Gentner-Scholarship of the BMBF

Software-based approach Optimization of existing UFO model: include know-how gained from dust samples (size distribution and material composition) to include adhesion Modification of UFO Buster software: implementation of a new algorithm respecting IP7 losses (elastic scattering products) to filter „fake“ UFO events Statistical analysis of UFO Buster data: comparison of run 1 and run 2, searching for correlations in special fills to understand physics behind release mechanism and dynamics in e-mag fields Co-Analyse dBLM data: if available the dBLMs provide bunch by bunch resolution of UFO events Investigate connection between UFO rate and SEY conditioning

Experimental approach UFO collection: extract original contamination from LHC beam screen (spare magnets) analyze it for chemical composition and size distribution to get hint on: origin, adhesive behavior, release mechanism, dynamics, removal Beam pipe mock-up: develop a vacuum setup which simulates the electric field inside the beam pipe and study particle behavior with laser to further understand dynamics insert this mock-up into a magnet and see how the dynamics change in B field Systematic UFO removal: investigate strategies to clean the LHC beam pipe from the contaminants Study of UFO adhesion force: vibration study: vacuum chamber with dusty beam screen and hammer with tunable force, laser particle counter to detect released UFOs

BLMTI.06L7.B1E10_TCP.C6L7.B1 3.99 E-2 in RS4

Loss signal/Threshold: 7.13 E-2 BLMQI.18L6.B1E10_MQ UFO timestamp 2016-05-18, 09:06:35 Loss signal/Threshold: 7.13 E-2 Losses in RS 4: 9.42 E-2

Loss signal/Threshold: 1.92E-2 BLMBI.26L5.B0T20_MBA-MBB_26L5 UFO timestamp 2016-05-27 05:22:30.0 Loss signal/Threshold: 1.92E-2 Losses in RS 4: 8.57E-3

TIMBER data for BLMBI.26L5.B0T20_MBA-MBB_26L5 LDB MDB