1. Introduction to the NPM for ESS Cold Linac
Cyrille Thomas
11 June, 2019

2. Layout
Introductive digression: Requirements, specification and instrument design
NPM: baseline and Cold Linac NPM baseline
Other instruments studied and discarded
Planning timeline of the project
Interfaces
Project summary

3. Profile Measurements Requirements
Level 4 requirement as given in DOORS for the Cold Linac Sections
Proton beam instrumentation shall function over a peak beam current range of 3 mA to 65 mA
Proton beam instrumentation shall function over a proton beam pulse length range of 5μs to ms
Unless specifically stated, all instrumentation shall be able to perform the measurements and report the relevant PV data at a repetition rate of 14 Hz
The transverse beam profile shall be measured with a total measurement error in the RMS extension of the beam of less than ±10%
The transverse beam profile shall be measured with a total measurement error in the 95% extension of the beam of less than ±10%
The transverse beam profile measurement shall have a dynamic range of 1000 …
These requirements do not constitute specification for the instrumentation
L5 requirements specify condition in which a requirement can be fulfilled

4. Translation towards instrument specs:
L4 Requirement 1,2,3:
Proton beam instrumentation shall function over a peak beam current range of 3 mA to 65 mA
Proton beam instrumentation shall function over a proton beam pulse length range of 5μs to ms
Unless specifically stated, all instrumentation shall be able to perform the measurements and report the relevant PV data at a repetition rate of 14 Hz
WS +
NPM
(3mA,3µs) -> 1011 proton per pulse
(65mA,50µs) -> 1013 proton per pulse*
(6mA,300µs) -> 1013 proton per pulse*
(65mA,2.98ms) -> 1015 proton per pulse
NPM: # event to be detected
Profile measured for each and every nominal pulses
Detection threshold for a measurement
+ WS does not produce a single pulse profile measurement
* NPM May not produce measurement for a single pulse
L5 requirements for the NPM specified through interfaces
NPM range of operation and performance to be determined in the detail design phase

5. Instrument design and performance
L4 requirement 4: beam size, s, with 10% error or less:
Instrument response spread function D:
Case with no correction from instrument model
Case with correction
Instrument Model is essential!
See Model of an IPM:
Investigation on Space Charge Perturbation to the Profile Measurement by Francesca Belloni s sm

6. Instrument Model: Example
X-ray pinholes camera with a range of apertures
25 (s)
100 (c)
50 (c)
30 (c)
25 (c)
20(c)
12 (c)
Raw images
PSF
Processed images
Knowledge of the Model!
Value reported of the emittance coupling used by feedback system to stabilized Diamond vertical emittance around 8pm.rad as requested by Science Division (initial nominal at 30pm.rad)

7. L4 requirement 5 and 6:
The transverse beam profile shall be measured with a total measurement error in the 95% extension of the beam of less than ±10%
The transverse beam profile measurement shall have a dynamic range of 1000
M0 = 29999
M1 =
s =
Skew =
Kurt. =
Gaussian!
Analogic and digitized signal:
Signal intensity and gain selection
Instrument in counting mode regime: 30x103 counts, 100 bin
# counts, noise level, single event signal discrimination

8. Requirement L4 and L5
For the Beam Instrumentation, L4 requirement essential to start the design of the instruments
L4 requirements guide the specifications to the instruments, and the technical implementation is specified by L5 requirements
L4 requirements set a good basis of discussion to reach the common objective to build, commission and operate the accelerator matching the L1,2,3 requirements
Appreciation of how L4 requirements can be match is part of the discussion between the partners and stakeholders

9. ESS Linac and NPMs
BIF
IPM
BIF
NPM:
Transverse profile measurement up to full power
Tuning and operation diagnostic
Commissioning tool: profile and measured size for matching beam and lattice parameters to the model predicted nominal values, emittance measurement and measure emittance growth
Operation: monitor beam nominal parameters
Performance:
Profile measurement per pulse (14Hz, nominal conditions)
Intra-pulse measurement bonus (highly desired)
Baseline:
BIF: 1st choice, everywhere it is possible: NPM type 1
IPM: where BIF cannot deliver expected performance: NPM type 2
See next Talk:
Accelerator Tuning and Beam Profile Measurements
From Dr. Yngve Levinsen (Beam Physics Section)

10. NPM for the Cold Linac
NPM baseline: Fluorescence based profile measurement:
Robust
Reliable
Low maintenance
Does not work in the Cold Linac Sections
10-9mbar, 1015 protons = 1-10 photon through an optical system
Another instrument is required: choice of ionisation based instrument:
10-9mbar, 1015 protons > 104 – 105 ions/electrons
Known instrument, IPM, installed on several proton accelerators in the world
Knowledge base
Possible collaboration

11. Other possible candidates:
Optical Diffraction Radiation:
Coherent signal, but at mm wavelength, difficult technology
Doesn’t provide direct shape measurement
Electron gun beam scanner:
Assume no correlation between long. and transverse planes in order to retrieve profile:
long. bunch size >> trans. bunch size
Doesn’t apply to ESS beam
Laser – vacuum residual gas interaction: time-resolved and/or spectroscopy techniques (many possible setups)
Great potential: 10-9mbar = 25x103 emitters / mm3 emitting coherently
Never been fully investigated except 1 case 15 years ago (absorption spectroscopy of Ar, B. Pottin PhD thesis, Univ. Paris Sud, 2001)
Yet to be done: full theoretical study, prototypes testing, further design, etc. to develop a mature instrument
Gas jet injection + BIF: not mature enough to be installed between cryo-cavities. Studies (BI and Vacuum) started at ESS to gain expertise …

12. NPM for the Cold Linac Project plan: Preliminary design:
Source studies: to understand the signal intensity as function of the gas species and for the possible readout systems
Space Charge studies: understand the ESS beam conditions and impact on the ions/electrons projection
Readout system to be selected and related performance of the NPM, taking into account radiation environment
Control integration and EPICS compliance
Maintenance estimates for the in-vacuum and out of vacuum parts of the system
Detail design:
Detail of the system baselined at PDR stage
Prototyping and performance proving
CDR date March 2018
Procurement, installation, integration, commissioning
Commissioning date: Beam on target on DumpL commissioning mid-2019

13. Interfaces
NPM is an instrument for the beam diagnostic, it has many interfaces:
Accelerator physics group, responsible for the definition of the tuning and operation nominal points
Vacuum group, since part of the instrument is in vacuum, and the main intensity directly depends on the good (but we ‘expect’ bad) vacuum chamber residual pressure
Linac Group in charge of the integration
ICS group for the control integration
Etc.
Communication with all these partners is critical
Contact and discussion in place with most partners (Vacuum, Mechanical Integration, Control Integration, Beam Physics, Safety, etc.

14. NPM: Project Summary Conceptual Design Detail Design PDR Production
Feasibility
Requirements
interfaces
Detail Design
Detail design (mechanical, electronic, etc.)
Performance demonstration
Prototyping
Production
Procurement
Assembling
Delivery
installation
Integration
commissioning
Handover to operation
PDR
CDR
SAR

15. 09: :15
General Introduction of NPM for ESS
Dr. Cyrille Thomas
09: :30
Accelerator Tuning and Beam Profile Measurements
Dr. Yngve Levinsen
09: :50
Introduction to the CEA Saclay Preliminary Design of the IPM
Mr. Jacques Marroncle
09: :20
Study of the Electric Field Uniformity
10: :40
Coffee Break
10: :25
Model of an IPM: Investigation on Space Charge Perturbation to the Profile Measurement
Dr. Francesca Belloni
11: :00
Source Signal Estimation and Foreseen Read-out System to Be Tested
Florian Benedetti (PhD)
12: :35
IPM Test Bench Design and Beam Test Strategy
12: :10
Lunch
14: :25
LWU Design and Integration of the NPM
Mr. Thomas Grandsaert
14: :50
Control Development and Integration Support for the Cold Linac NPM
TBD
14: :05
Building Block for the Cold Linac NPM
Mr. Hinko Kocevar
15: :40
NPM Design and Production Timeline
15: :00
16: :30
Closed Session