Design and Engineering�of Modern Beam Diagnostics�

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Silvia Zorzetti (Fermilab)

Randy Thurman-Keup (Fermilab)

Manfred Wendt (CERN)

Evan Milton (Fermilab)

U.S. Particle Accelerator School USPAS 2024

Hampton (VA), January 29^th – February 2^nd, 2024

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January 29^th – February 2^nd , 2024, USPAS Hampton (VA), U.S.A. – Modern Beam Diagnostics, Introduction – M. Wendt

Introduction

• What is “Beam Instrumentation”?
• We provide the “eyes” to “visualize” the beam for the accelerator operators
• We monitor and characterize the beam, and deliver the beam parameters
• An accelerator can never be better than the beam instruments measuring its performance!
• What does work in beam instrumentation entail?
• Design, construction & operation of instruments �to observe charge particle beams in an accelerator or a beam-line
• R&D to find new or improve existing techniques to meet new requirements
• This includes the following, incomplete list of disciplines
• Applied & accelerator physics; mechanical, electronics & software engineering
• “Beam Instrumentation” vs. “Beam Diagnostics”
• Basically the same, but sometimes
• Beam instrumentation refers to the specific beam instruments
• R&D, engineering, prototyping, and commissioning of a beam instrument
• Beam diagnostics applies and uses the beam instruments in the accelerator
• Utilized a variety of beam instrumentation and manipulation techniques to characterize the beam parameters, �e.g. emittance, chromaticity, etc.

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January 29^th – February 2^nd , 2024, USPAS Hampton (VA), U.S.A. – Modern Beam Diagnostics, Introduction – M. Wendt

Beam & Machine Parameters

• Beam intensity (& lifetime in a storage ring / collider)
• Beam charge (or current in a ring), total (DC) or bunch-by-bunch
• Broadband beam intensity monitors also serve as longitudinal bunch profile monitor
• Also used as beam “quality” monitor and for timing applications
• Beam orbit (ring) or trajectory (linac / transport-line)
• Based on beam position monitors (BPM) located along the accelerator
• BPMs also serve for betatron & synchrotron tune, coupling, chromaticity, momentum �and many other beam and machine measurements
• Also provides the source signal of a variety of beam feedback systems
• Beam commissioning, beam optics measurements and trouble shooting
• Transversal / longitudinal beam profiles
• Particle distribution or size of the beam / bunch
• From which we can deduce the beam emittance, beam energy, energy spread �and many other beam and machine parameters
• Beam losses
• Important for superconducting and high brightness machines
• However, not covered in this course

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January 29^th – February 2^nd , 2024, USPAS Hampton (VA), U.S.A. – Modern Beam Diagnostics, Introduction – M. Wendt

General Beam Instrumentation Challenges

• Large physical size of the collider
• # of components, reliability, costs
• E.g. replace copper cable by optical fibers
• Harsh environment
• Ionizing radiation (effects on electronic components, insulators, other materials)
• ultra-high vacuum (UHV), cryogenic temperatures (superconductivity)
• RF feedthroughs, cables, cold beam pickups & BLMs
• Higher-order modes (HOM) & wakefield effects
• RF heating of beam pickups and in-vacuum components
• Impedance budget, instabilities
• High brilliance, high power beams
• Non-invasive monitoring of all relevant machine parameters!
• Monitoring / damping of beam instabilities
• Head-tail, e-cloud, etc.
• Be prepared for changes!
• Beam formatting , e.g. bunch intensity, bunch spacing, etc.
• Beam energy
• Beam optics and layout near the IP: High luminosity upgrade HL-LHC
• Machine protection!
• High damage potential of high intensity, high brightness beams.

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January 29^th – February 2^nd , 2024, USPAS Hampton (VA), U.S.A. – Modern Beam Diagnostics, Introduction – M. Wendt

Beam Monitors

• Beam pickup
• Often part of the accelerator beam pipe / vacuum system
• Electromagnetic, optical, secondaries, etc.
• Preferable non- or minimum invasive
• Read-out system
• Electronics for signal conditioning, parameter extraction and data acquisition
• Test and/or calibration signals
• Infrastructure
• Timing, synchronization
• Cabling, power supplies, cooling, etc.
• Data acquisition (DAQ), �network communication, controls
• Environmental conditions
• Ionizing radiation, cryogenic temperatures, ultra-high vacuum (UHV), etc.

Focus

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January 29^th – February 2^nd , 2024, USPAS Hampton (VA), U.S.A. – Modern Beam Diagnostics, Introduction – M. Wendt

Qualification of our Beam Measurements?

• Accuracy, Precision, Resolution
• Sometimes confusing terms in the day-to-day language
• Accuracy ⇒ How close is our measured value to the true value
• Sometimes we distinguish between absolute and relative accuracy
• Precision ⇒ How good can we reproduce a measurement
• Resolution ⇒ What is the smallest difference can detect

• Example: BPMs
• Mechanical and electronics offset, gain factors & calibration ⇒ absolute and relative accuracy
• Bandwidth, input amplifier noise, power supply ripple, clock jitter, ADC ENOBs ⇒ resolution
• Temperature drift effects, aging of components ⇒ precision

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January 29^th – February 2^nd , 2024, USPAS Hampton (VA), U.S.A. – Modern Beam Diagnostics, Introduction – M. Wendt

This Course…

• Restart after COVID
• Course was given in 2019, as a fresh assembly 10 years after a 2009 lecture
• We try to cover many topics and aspects on beam instrumentation and diagnostics
• With material from workshops, conferences, and other schools (CAS, JUAS).
• Thanks to our colleagues sharing their material!
• We try to give a wide range, however still incomplete, view on modern, �mostly non-invasive beam instrumentation (BI)
• We selected those types of beam instruments and techniques, for we feel rather familiar, �competent and experienced with.
• Our focus is on the physics and engineering of beam pickup
• Read-out and data acquisition technologies change very rapidly and may be outdated too quickly
• Please apologize if we don’t cover the type of beam instrument which is of particular interest for you.
• Sorry, we cannot cover everything.
• We cover a mix of applied physics, engineering and data processing �in the frame of modern beam diagnostics
• Please note, we the lecturers, have different background and experience
• This is our 2^nd time we give this course
• Still, there may be errors, inconsistencies, misleading and/or incomplete points.�Please try to apologize!
• You feedback is very welcome and important!

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January 29^th – February 2^nd , 2024, USPAS Hampton (VA), U.S.A. – Modern Beam Diagnostics, Introduction – M. Wendt

Course Outline

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January 29^th – February 2^nd , 2024, USPAS Hampton (VA), U.S.A. – Modern Beam Diagnostics, Introduction – M. Wendt

A few practical remarks

• Information
• All relevant information will be uploaded on Google drive:�https://drive.google.com/drive/folders/1cFV0C_pdtqSvamDlqZX2GF1Py8rD_JoI
• Randy compiled a webpage for easier access to the core material:�https://sites.google.com/view/uspas-dembd-2024/home
• Exam grade will be based on
• 50 % final exam (Friday),
• 20 % homework,
• 20 % class participation, including group exercise and hands-on training,
• 10 % computer exercises
• We need to be flexible
• If required, we may have to make minor changes on the schedule…
• …in particular in the afternoons to add additional time for some unfinished lecture parts
• We need your participation!
• Please ask questions, don’t be shy!
• This course is for you, so please ask, and we try to answer to the best of our knowledge

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January 29^th – February 2^nd , 2024, USPAS Hampton (VA), U.S.A. – Modern Beam Diagnostics, Introduction – M. Wendt

Backup slides

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January 29^th – February 2^nd , 2024, USPAS Hampton (VA), U.S.A. – Modern Beam Diagnostics, Introduction – M. Wendt

Beam Characterization

• Beam intensity
• Beam & bunch currents, beam lifetime, abort gap
• Beam orbit and position – based of beam position monitors (BPM)
• BPMs with turn-by-turn and high resolution orbit capabilities
• Key element for beam optics studies and verification
• Beam / bunch feedback systems
• Beam orbit, bunch-by-bunch, luminosity feedback, crabbing and noise FBs, beam energy
• Bunch-by-bunch BPMs for technical interlocks (machine protection)
• High resolution BPMs
• E.g. integrated in the collimator jaws (LHC)
• Tune and instabilities
• No/minimum beam excitation, single-bunch (gated) tune detection
• Tune feedback
• Beam profile (longitudinal and transverse), beam size and halo
• Non/minimum invasive methods
• Emittance, chromaticity, coupling, etc.
• Beam diagnostics measurements
• Beam loss detection – based on beam loss monitors (BLM)
• Key element of the machine protection system (MPS)

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January 29^th – February 2^nd , 2024, USPAS Hampton (VA), U.S.A. – Modern Beam Diagnostics, Introduction – M. Wendt