IBIC2023 - List of Authors (Fisher, A.S.)

Paper	Title	Page
TU3I01	Commissioning of the LCLS-II Machine Protection System for MHz CW Beams	154
	J.A. Mock, A.S. Fisher, R.T. Herbst, P. Krejcik, L. Sapozhnikov SLAC, Menlo Park, California, USA
	Beam power at the LCLS-II linac and FEL can be as high as several hundered kW with CW beam rates up to 1 MHz. The new MPS has a latency of less than 100 µs to prevent damage when a fault or beam loss is detected. The MPS architecture encompasses the multiple FEL beamlines served by the SC linac and can mitigate a fault in one beamline without impacting the beam rate in a neighboring beamline. The MPS receives inputs from various devices including loss monitors and charge monitors as well as magnet power supplies and BPMs to pre-emptively turn of the beam if a fault condition is detected. Link nodes distributed around the facility gather the input data and stream it back to a central processor that signals other link nodes connected to beam rate control devices. Commmissioning and experience with the new system will be described.
	Slides TU3I01 [4.239 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-IBIC2023-TU3I01
About •	Received ※ 06 September 2023 — Revised ※ 08 September 2023 — Accepted ※ 12 September 2023 — Issue date ※ 25 September 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP005	Commissioning the Beam-Loss Monitoring System of the LCLS Superconducting Linac	187
	A.S. Fisher, N. Balakrishnan, G.W. Brown, E.P. Chin, W.G. Cobau, J.E. Dusatko, B.T. Jacobson, S. Kwon, J.A. Mock, J. Park, J. Pigula, E. Rodriguez, J.I.D. Rudolph, D. Sanchez, L. Sapozhnikov, J.J. Welch SLAC, Menlo Park, California, USA
	A 4-GeV superconducting linac has been added to the LCLS x-ray FEL facility at SLAC. Its 120-kW, 1-MHz beam requires new beam-loss monitors (BLMs) for radiation protection, machine protection, and diagnostics. Long radiation-hard optical fibres span the full 4 km from the electron gun of the SC linac to the final beam dump. Diamond detectors at anticipated loss points provide local protection. Detector signals are continuously integrated with a 500-ms time constant and compared to a loss threshold. If crossed, the beam is halted within 0.1 ms. Commissioning began in March 2022 with the 100-MeV injector and with RF processing of the cryomodules. At IBIC 2022 last September, we presented commissioning results from the injector BLMs. In October, the beam passed through the full linac and the bypass transport line above the LCLS copper linac, stopping at an intermediate dump. In August it continued through the soft x-ray undulator and achieved first lasing. Here we present BLM commissioning at energies up to 4 GeV and rates up to 100 kHz. We discuss measurements and software using the fast diagnostic-waveform output to localize beam losses and to detect wire-scanner signals.
	Poster TUP005 [2.620 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-IBIC2023-TUP005
About •	Received ※ 06 September 2023 — Revised ※ 08 September 2023 — Accepted ※ 13 September 2023 — Issue date ※ 27 September 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP006	Simulation and Shot-by-Shot Monitoring of Linac Beam Halo	191
	A.S. Fisher, M. Bai, T. Frosio, A. Ratti, J. Smedley, J. Wu SLAC, Menlo Park, California, USA I.S. Mostafanezhad, B. Rotter Nalu Scientific, LLC, Honolulu, USA
	FELs require a reproducible distribution of the bunch core at the undulator entrance for robust and reliable lasing. However, various mechanisms drive particles from the core to form a beam halo, which can scrape the beampipe of the undulator and damage its magnets. Collimators can trim the halo, but at the 1-MHz repetition rate of SLAC’s LCLS-II superconducting linac, the collimator jaws can be activated and damaged. The Machine Protection System (MPS) can detect excessive radiation and halt the beam, but repeated MPS trips lead to significant downtime. Halo control begins by studying its structure, formation, and evolution, using a sensitive halo monitor. To that end, we are developing a pixellated diamond sensor. Diamond offers a dynamic range of up to 7 orders of magnitude, extending from the edge of the core to the faint halo expected at greater distances. Nalu Scientific has developed fast electronics for high-rate shot-by-shot readout. Initial tests are starting with a prototype 16-pixel sensor at the beam dump of SLAC’s FACET-II test facility. The tests and simulations will guide more elaborate sensor designs.
	Poster TUP006 [2.602 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-IBIC2023-TUP006
About •	Received ※ 07 September 2023 — Revised ※ 08 September 2023 — Accepted ※ 12 September 2023 — Issue date ※ 19 September 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP042	Nano-Amp Beam Current Diagnostic for Linac-to-ESA (LESA) Beamline	285
	S.T. Littleton Stanford University, Stanford, California, USA A.S. Fisher, C. Huang, T.O. Raubenheimer SLAC, Menlo Park, California, USA
	The LESA beamline is designed to transport dark current from the LCLS-II and LCLS-II-HE superconducting linacs to the End Station A for various fixed target experiments. The primary experiment is expected to be the Light Dark Matter eXperiment (LDMX) which required beam currents of a few pA. The operation of the beam line much be parasitic to the LCLS-II / LCLS-II-HE FEL operation. The dark current in the LCLS-II is expected to be at the nA-level which will be below the resolution of most of the LCLS-II diagnostics (it will be degraded before the experiments as necessary). This paper will describe a possible non-destructive diagnostic using synchrotron radiation that could be applied at multiple locations along the LCLS-II and the LESA beamline.
DOI •	reference for this paper ※ doi:10.18429/JACoW-IBIC2023-TUP042
About •	Received ※ 07 September 2023 — Revised ※ 11 September 2023 — Accepted ※ 13 September 2023 — Issue date ※ 16 September 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Commissioning of the LCLS-II Machine Protection System for MHz CW Beams

154

J.A. Mock, A.S. Fisher, R.T. Herbst, P. Krejcik, L. Sapozhnikov
SLAC, Menlo Park, California, USA

Beam power at the LCLS-II linac and FEL can be as high as several hundered kW with CW beam rates up to 1 MHz. The new MPS has a latency of less than 100 µs to prevent damage when a fault or beam loss is detected. The MPS architecture encompasses the multiple FEL beamlines served by the SC linac and can mitigate a fault in one beamline without impacting the beam rate in a neighboring beamline. The MPS receives inputs from various devices including loss monitors and charge monitors as well as magnet power supplies and BPMs to pre-emptively turn of the beam if a fault condition is detected. Link nodes distributed around the facility gather the input data and stream it back to a central processor that signals other link nodes connected to beam rate control devices. Commmissioning and experience with the new system will be described.

Slides TU3I01 [4.239 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-IBIC2023-TU3I01

About •

Received ※ 06 September 2023 — Revised ※ 08 September 2023 — Accepted ※ 12 September 2023 — Issue date ※ 25 September 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP005

Commissioning the Beam-Loss Monitoring System of the LCLS Superconducting Linac

187

A.S. Fisher, N. Balakrishnan, G.W. Brown, E.P. Chin, W.G. Cobau, J.E. Dusatko, B.T. Jacobson, S. Kwon, J.A. Mock, J. Park, J. Pigula, E. Rodriguez, J.I.D. Rudolph, D. Sanchez, L. Sapozhnikov, J.J. Welch
SLAC, Menlo Park, California, USA

A 4-GeV superconducting linac has been added to the LCLS x-ray FEL facility at SLAC. Its 120-kW, 1-MHz beam requires new beam-loss monitors (BLMs) for radiation protection, machine protection, and diagnostics. Long radiation-hard optical fibres span the full 4 km from the electron gun of the SC linac to the final beam dump. Diamond detectors at anticipated loss points provide local protection. Detector signals are continuously integrated with a 500-ms time constant and compared to a loss threshold. If crossed, the beam is halted within 0.1 ms. Commissioning began in March 2022 with the 100-MeV injector and with RF processing of the cryomodules. At IBIC 2022 last September, we presented commissioning results from the injector BLMs. In October, the beam passed through the full linac and the bypass transport line above the LCLS copper linac, stopping at an intermediate dump. In August it continued through the soft x-ray undulator and achieved first lasing. Here we present BLM commissioning at energies up to 4 GeV and rates up to 100 kHz. We discuss measurements and software using the fast diagnostic-waveform output to localize beam losses and to detect wire-scanner signals.

Poster TUP005 [2.620 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-IBIC2023-TUP005

About •

Received ※ 06 September 2023 — Revised ※ 08 September 2023 — Accepted ※ 13 September 2023 — Issue date ※ 27 September 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP006

Simulation and Shot-by-Shot Monitoring of Linac Beam Halo

191

A.S. Fisher, M. Bai, T. Frosio, A. Ratti, J. Smedley, J. Wu
SLAC, Menlo Park, California, USA
I.S. Mostafanezhad, B. Rotter
Nalu Scientific, LLC, Honolulu, USA

FELs require a reproducible distribution of the bunch core at the undulator entrance for robust and reliable lasing. However, various mechanisms drive particles from the core to form a beam halo, which can scrape the beampipe of the undulator and damage its magnets. Collimators can trim the halo, but at the 1-MHz repetition rate of SLAC’s LCLS-II superconducting linac, the collimator jaws can be activated and damaged. The Machine Protection System (MPS) can detect excessive radiation and halt the beam, but repeated MPS trips lead to significant downtime. Halo control begins by studying its structure, formation, and evolution, using a sensitive halo monitor. To that end, we are developing a pixellated diamond sensor. Diamond offers a dynamic range of up to 7 orders of magnitude, extending from the edge of the core to the faint halo expected at greater distances. Nalu Scientific has developed fast electronics for high-rate shot-by-shot readout. Initial tests are starting with a prototype 16-pixel sensor at the beam dump of SLAC’s FACET-II test facility. The tests and simulations will guide more elaborate sensor designs.

Poster TUP006 [2.602 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-IBIC2023-TUP006

About •

Received ※ 07 September 2023 — Revised ※ 08 September 2023 — Accepted ※ 12 September 2023 — Issue date ※ 19 September 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP042

Nano-Amp Beam Current Diagnostic for Linac-to-ESA (LESA) Beamline

285

S.T. Littleton
Stanford University, Stanford, California, USA
A.S. Fisher, C. Huang, T.O. Raubenheimer
SLAC, Menlo Park, California, USA

The LESA beamline is designed to transport dark current from the LCLS-II and LCLS-II-HE superconducting linacs to the End Station A for various fixed target experiments. The primary experiment is expected to be the Light Dark Matter eXperiment (LDMX) which required beam currents of a few pA. The operation of the beam line much be parasitic to the LCLS-II / LCLS-II-HE FEL operation. The dark current in the LCLS-II is expected to be at the nA-level which will be below the resolution of most of the LCLS-II diagnostics (it will be degraded before the experiments as necessary). This paper will describe a possible non-destructive diagnostic using synchrotron radiation that could be applied at multiple locations along the LCLS-II and the LESA beamline.

DOI •

reference for this paper ※ doi:10.18429/JACoW-IBIC2023-TUP042

About •

Received ※ 07 September 2023 — Revised ※ 11 September 2023 — Accepted ※ 13 September 2023 — Issue date ※ 16 September 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)