ESS Beam

Diagnostics

Overview

Andreas Jansson, ESS/BI Group

IBIC12, Tsukuba, Japan

2012-10-3

2

Overview

• Overview of ESS Project

• Baseline diagnostics layout

• “Bread-and-butter” diagnostics systems

• Some particular challenges

Berkeley 37-inch cyclotron

350 mCi

Ra-Be source

Chadwick

1930 1970 1980 1990 2000 2010 2020

105

1010

1015

1020

1

ISIS

Pulsed Sources

ZINP-P

ZINP-P/

KENS WNR

IPNS

ILL

X-10

CP-2

Steady State Sources

HFBR

HFIR NRU MTR

NRX

CP-1

1940 1950 1960

Effective therm

al neutr

on f

lux n

/cm

2-s

(Updated from Neutron Scattering, K. Skold and D. L. Price, eds., Academic Press, 1986)

Evolution of the performance of neutron sources

FRM-II

SINQ

SNS

ESS - the neutron source for tomorrow

ESS

Why Neutrons?

Cs Zr Mn S O C Li H

X-rays

Neutrons

- Thermal neutrons have a wavelength (2 Å) similar to inter-atomic distances, and an energy (20 meV) similar to elementary excitations in solids.

- Simultaneous information on the structure and dynamics of materials.

- Cross section varies between elements and even between different isotopes of the same element.

- In particular, hydrogen has a large neutron cross section, different from deuterium.

- Neutrons probe the bulk of the sample, and not only its surface.

- Since neutrons penetrate matter easily, neutron scattering can be performed

with samples stored in all sorts of sample environment: Cryostats, magnets, furnaces, pressure cells, etc.

- The neutron magnetic moment makes neutrons scatter from magnetic structures or magnetic field gradients.

From K. Lefmann

5

Details/Resolution

Intensity opens new possibilities

Complexity/ Count-rate

ESS intensity allows studies of

– complex materials

– weak signals

– important details

– time dependent phenomena

Sweden, Denmark and Norway

cover 50% of construction cost

Remaining 50% from European

partners

Letters of intent from 17 European states

Multilateral MoU for pre-construction

signed in Paris 11 Feb 2012

International Collaboration

Where is ESS?

Where is ESS?

Particle species p Energy 2.5 GeV Current 50 mA Average power 5 MW Peak power 125 MW Pulse length 2.86 ms Rep rate 14 Hz Max cavity surface field 40 MV/m Operating time 5200 h/year Reliability (all facility) 95%

FDSL_2012_05_15

ESS Linac Parameters

Cold neutrons – Long Pulse

• Up to 90% of neutron experiments use cold neutrons

• Pulsed cold neutrons always come as long pulses as a result of the

moderation process

• No compressor ring required, major difference from earlier ESS proposal

F. Mezei, NIM A, 2006

Lab Eout (MeV) Betaout Length (m) Temp (K) Freq (MHz)

Ion source + LEBT Catania 0.075 0.01 4.6 300 -

RFQ Saclay 3 0.08 5.0 300 352.21

MEBT Bilbao 3 0.08 3.5 300 352.21

DTL Legnaro 79 0.39 32.5 300 352.21

Spoke cavities Orsay 201 0.57 58.6 2 352.21

Medium-beta ellipticals Saclay 623 0.80 113.9 2 704.42

High-beta ellipticals Saclay 2500 0.96 227.9 2 704.42

HEBT Aarhus 2500 0.96 159.2 300 -

Spoke resonators Medium-beta ellipticals High-beta ellipticals

Cells per cavity 3 5 5

Cavities per cryomodule 2 4 4

Number of cryomodules 14 15 30

Linac Layout

ESS Linac Optics

13

Linac Component Designs

LNL – 6 September 2012Paolo MEREU – DTL Meeting

DTL

Spoke Cryomodule

Elliptical Cavity Cryomodule

Warm Quad

Doublet Unit

14

Tunnel & RF Gallery Layout

Frequency (MHz)

No. of couplers

Max power (kW)

RFQ 352.21 1 900

DTL 352.21 4 2150

Spokes 352.21 28 280

Medium betas 704.42 60 560

High betas 704.42 129 850

Decision to have a single

integrated control system

for ESS:

- EPICS-based

- ITER control-box

concept

Two hardware prototyping

platforms selected:

• cPCIe

• uTCA.4

Integrated Control System

ESS Master Schedule

200

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1

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2

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ESS Program

Phases, Gates and

Milestones

Program level

Accelerator

Target

Instruments

Conventional

Facilities

Program

Initiation Program Set-up Delivery of Contsruction phase

PG 3

PG 2

PG 1

PG 4

Full beam power

on target

Design Update

Prepare to Build

Construction

Technical Design Report

Design Update

Prepare to Build

Construction

Concepual Design

Installation 1-22

Installation

Design Update

Site preparation

Construction

# 7

List

Ground Break

Pre-construction phase

Operations

Installation

Design and Manufacturing 22 instruments

Construction

First Building

First Neutrons

to Instruments

losure

Pre Construction Report

The ESS Site Today

The ESS Site Today

The ESS Site Today

The ESS Site Today

17

New CEO, announced today

James Yeck

Most recently:

Assistant Project Director for Conventional Construction at NSLS-II

and Director of IceCube,

previously Project Director for US-LHC, and

DOE Project Manager for RHIC construction project

Starting at ESS January 1, taking over as CEO March 1

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… and now, to the diagnostics part…

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LEBT

2 BCMs

1 Slit + 2 H/V Grids

1 Faraday Cup

Viewports (for profile)

20

MEBT

6 BPMs

4 BCMs (2 fast, 2 slow)

1 Slit + 1 H/V Grid

1 Faraday Cup

4 Wire Scanners

2 Non-invasive profile devices (viewports w camera)

2 Halo Monitors

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DTL

LNL – 6 September 2012Paolo MEREU – DTL Meeting

12 BLMs (4 ICs, 4 Fast BLMs, 4 Neutron Detectors)

8 BPMs

6 BCMs (5 slow, 1 fast)

4 Faraday Cups

4 Wire Scanners

4 Non-invasive profile devices (viewports w camera)

1 BSM

1 Halo Monitor

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Cold Linac and upgrade space

3 BLMs per cell

1 BPM per quadrupole

1 BCM per transition between main sections

4 Wire-scanners co-located with non-invasive profile monitors at each transition

4 BSMs at each transition

Example:Spoke Section

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Target and Dump lines

BLM and BPM at most quads

BCMs to verify beam destination

WS and non-invasive profile at octupoles

Redundant target profile diagnostics

Accelerator to Target Line 25 mm

200 mm

• Simulation with 500,000 particles

Simulation data: Aarhus

Target Diagnostics Layout

• Upstream wire scanners to measure emittance (not shown here)

• BCM above:

– Used to normalize beam density measurements

– Beam accounting (power on target, total energy delivered, etc)

• Redundant measurements at proton beam window and target:

– Halo: Halo monitoring via thermocouple assemblies

– Img: Imaging (luminescent coatings on Proton Beam Window and Target)

– NPM: Non-Invasive Profile monitor (He gas luminescence)

– Grid: SEM in vacuum and ionization in Helium

He at ~1 atm vacuum

Layout of Target Monolith

Target shaft

Target

diagnostics

(no details yet)

Target wheel

Beam Instrumentation Plug

• Optics (upstream,

downstream, H and V)

• H and V grid

• halo

PBW:

Coating (~100 C)

H and V grid

halo

PBW

plug

He-valve

plug

Access to water

cooled

shielding blocks

(if necessary)

Coating on

target (<200 C) 4.4

meters

Optical and

signal path

Drawing: FZ Jülich

Beam Loss

If lost in one spot, the beam can

melt steel in a few microseconds

BLM system needs to detect large

losses in 2us (10us in cold linac)

For small continuous losses, BLMs should

have sensitivity to detect losses leading

to activaton of 1% of the hand-on limit

(~0.01W/m)

Ionization Chamber will be main detector type.

(LHC or SNS type could be used)

Some fast monitors (scintillator, diamond) and

neutron detectors will be used

Beam Loss

• Simulations ongoing to optimize exact detector location

• Have Marie Curie Fellow (through oPAC network) to work on this

Loss location = middle of first quadrupole

Loss angle = 1.5 mrad

Loss intensity = 10^12 protons/sec

28

Beam Current

• Plan to use mainly ACCTs, with some FCTs for bunch studies

• Beam current should be measured to 1%.

• Differential BCM measurements will be used to complement BLMs for

beam loss in the low energy section -> same response time

requirements as BLMs

BPMs

• Need a sensitvity of <0.1mm for

position and 1 degree for

phase.

• Plan to use mostly buttons,

similar to those in E-XFEL

• SNS-like stripline in DTL

• Prototyping electronics in

uTCA.4 (one of two prototyping

platforms agreed on with

Controls Group).

BPMs

• Need a sensitvity of <0.1mm for

position and 1 degree for

phase.

• Plan to use mostly buttons,

similar to those in E-XFEL

• SNS-like stripline in DTL

• Prototyping electronics in

uTCA.4 (one of two prototyping

platforms agreed on with

Controls Group).

BPM Signals

Preliminary studies (using E-XFEL button size) show that button signal gives

adequate sensitivity for production and diagnostics beam for nominal bunch length.

During tune-up of the cold linac, beam will be transported long distances without

longitudinal focussing. The BPM system should be able to provide some position

information to allow to center debunched beam. May need larger buttons for this.

BPM Signals

Preliminary studies (using E-XFEL button size) show that button signal gives

adequate sensitivity for production and diagnostics beam for nominal bunch length.

During tune-up of the cold linac, beam will be transported long distances without

longitudinal focussing. The BPM system should be able to provide some position

information to allow to center debunched beam. May need larger buttons for this.

BPM Signals

Preliminary studies (using E-XFEL button size) show that button signal gives

adequate sensitivity for production and diagnostics beam for nominal bunch length.

During tune-up of the cold linac, beam will be transported long distances without

longitudinal focussing. The BPM system should be able to provide some position

information to allow to center debunched beam. May need larger buttons for this.

• Preliminary ANSYS simulations studies show that

the LEBT slits can be used with the full production

beam.

• TZM, graphite, tungsten are possible materials.

For MEBT slits, beam pulse must be reduced to 50 μs

Short available drift space leads to challenging SEM wire pitch (0.1mm).

Maximum temperature on a graphite slit for different slit angle and

pulse length, the mechanical limits of graphite is around 1600K

Emittance Measurement

• Carbon (33 μm) is the primary choice for wire scanner in

warm linac

In MEBT, beam pulse has to

reduced to 50 μs in order to

avoid thermionic emission and

wire damages

In the DTL the stopping power

is lower and a pulse length of

100 μs can be used.

Maximum temperature on a carbon wire during the slow tuning

mode (1Hz, 50 mA, 100 μs) at the exit of the first DTL tank (beam

sizes are 2 mm in both planes).

Maximum temperature on a carbon wire installed in

the MEBT (1Hz, 50 mA, 50 μs) .

Warm Linac Wire Scanners

Cold Linac Wire Scanners

• Carbon wires are not allowed in cold linac!

• 20 μm tungsten wires are considered.

• Expect no issue with temperature in the cold linac

Estimation of the temperature has been done

assuming σx=σy= 2 mm, with a beam energy of

80 MeV (no acceleration from the

superconducting cavity)

At around 2 GeV, the stopping power reaches its

minimum, assuming the same beam sizes, the

expected temperature are:

• 850 K during the fast tuning mode

• 950 K during the slow tuning mode

Maximum temperature during the fast tuning mode

Maximum temperature during the slow tuning mode

Wire Scanner signal

• Below the pion production threshold: measure secondary emission

– low level of signal above 100 MeV

• Above threshold, detect shower with scintillator

– the geometry of the detector can affect the beam profile reconstruction

• SCL Wire scanner will be used with care, for initial commissioning and for calibration of non-invasive method

Maximum expected current on the wire in function of the beam energy

in SEM mode for carbon wire (black line), tungsten wire (red line) and

in shower mode (blue dots).

Scintillator geometry, in green the

scintillator with the light guide (black

line) .and in grey the beam pipe

Energy deposition on the 4 scintillators in function of the wire

position (E=1GeV)

Non-invasive profile

• Want non-invasive monitor of beam

profile during neutron production

– Co-located with WS for cross-

calibration

• No sync light, and lasers don’t work

on protons …

• Methods under consideration

– Luminescence

– Ionization profile

– Electron/Ion beam scanner

• Recently started tests of luminesce

yield in the SNS HEBT

• Candidate Halo Methods:

– Wire Scanner

• can be used only at low energy where

the secondary emission signal is high

– Wire Scanner with telescope

• can be used only in the HEBT due to

the lake on space in the Linac

– Diamond

• The radiation could be an issue

– Cherenkov fiber scanner

• The radiation could be an issue

• MEBT Scrapers and collimators will also be

instrumented

• Thermocouples at windows and target

Diamond based detector used at spring8

for halo measurement (more detail in

TUPB24, DIPAC09, Basel)

Principe of the telescope in counting mode

Halo Measurement

Bunch Length

• Bunch length measurement in proton linacs is

challenging (short bunch, low beta).

• Feschenko style monitors will be used (several

versions has been proposed and developed)

• Plan topical workshop at ESS in Lund (tentatively

week of January 14th).

Downloaded 01 Dec 2009 to 130.199.3.130. Redistribution subject to AIP license or copyright; see http://proceedings.aip.org/proceedings/cpcr.jsp

Target monitoring

• Plan to use coat target and

window as at SNS

• Proton Beam Window is the

most critical

– Highest current density

• Also the most challenging

– Very thin, SNS style

luminescent coating

would add significant

mass

– Need coating R&D 39

96 CHAPTER 4. ACCELERATOR

Figure 4.132: Particle density plots on the PBW and the target. Notice also the horizontal and verticalbeam profi les on a linear scale.

target will nominally be exposed to a peak current density of 52 µA/cm 2 , whereas the PBW will be hitby a maximum current density of 84 µA/cm 2 , in both cases scaled to an average beam current of 2 mA.As a reference, a peak current density of 250 µA/cm 2 would result from a Gaussian beam without anyflattening. The fixed collimator will in the present scenario intercept 8.3 kW of beam power.

L osses and ap er tu res.

Tails in the beam may lead to losses unless the apertures are sufficiently large. On the other hand, magnetapertures drive the cost and have to be optimized. I n Fig. 4.133 the transverse power loss isocontours inboth planes together with the apertures in the magnets and vacuum chambers are shown. W e observe theabsence of beam losses, which with the present statistics correspond to power levels of less than 10 W .Notice in particular the very large aperture needed in front of the fixed collimator. Furthermore weobserve the reduced apertures in the octupoles as compared to the quadrupoles in general. F inally, thelast quadrupole triplet will have even larger apertures due to the expansion of the beam on the target.

B eam l in es for tu n in g b eam dum ps.

During initial setting-up of the ESS accelerator, and also during startup after shutdowns, a straightbeamline following the S1 line will transport the beam to a commissioning beam dump. This dump isdesigned for 50 kW , and a quadrupole doublet will expand the beam to 12.5 mm RMS on the dump. Inparticular during the initial commissioning of the linac with many phase scans of the cavities, this beamwill impinge on the target with varying energies and energy spreads.

A diagnostic line will transport the beam to a second tuning beam dump. The beamline is designedwith a large ratio between dispersion and betafunction, and hence the energy spread of the beam can bemeasured directly using profi le monitors. Such measurements are otherwise not available. The line willalso include a quadrupole expansion of the beam to the planned 50 kW beam dump. A beam plug (gammablocker) will be inserted in front of the dumps during maintenance personnel access to the linac tunnel.

4.6.2 Col l im ation

Comprehensive simulations of the beam transport from the linac to the target have been performed, butclearly some contingency has to be added in the present technical design of the components. In particular

96

Figure 4.128: Particle density plots on the PBW and the target. Notice also the horizontal and verticalbeam profi les on a linear scale.

Notice in particular the very large aperture needed in front of the fixed collimator. Furthermore weobserve the reduced apertures in the octupoles as compared to the quadrupoles in general. F inally, thelast quadrupole triplet will have even larger apertures due to the expansion of the beam on the target.

B eam l in es for tu n in g b eam dum ps.

During initial setting-up of the ESS accelerator, and also during startup after shutdowns, a straightbeamline following the S1 line will transport the beam to a commissioning beam dump. This dump isdesigned for 50 kW , and a quadrupole doublet will expand the beam to 12.5 mm RMS on the dump. Inparticular during the initial commissioning of the linac with many phase scans of the cavities, this beamwill impinge on the target with varying energies and energy spreads.

A diagnostic line will transport the beam to a second tuning beam dump. The beamline is designedwith a large ratio between dispersion and betafunction, and hence the energy spread of the beam can bemeasured directly using profi le monitors. Such measurements are otherwise not available. The line willalso include a quadrupole expansion of the beam to the planned 50 kW beam dump. A beam plug (gammablocker) will be inserted in front of the dumps during maintenance personnel access to the linac tunnel.

4.6.2 Col l im ation

Comprehensive simulations of the beam transport from the linac to the target have been performed, butclearly some contingency has to be added in the present technical design of the components. I n particularthe power content of the tails of the beam is vital as too much beam power might damage componentsand make maintenance difficult.

Two collimator systems will be installed in the HEBT . The fi rst, as a precaution, will be able to capturelarge-amplitude particles in beam with a system of transverse movable collimators. Two systems with anappropriate phase advance (of around 90 degrees for halo particles) between are needed to perform aneffective collimation. Each system will be designed to capture a few kW of beam power with a collimationefficiency in the order of % . The other system will be a fixed collimator. As described above, the octupolesin the S3 section will produce a flat beam distribution at the expense of sending large-amplitude haloparticles to even larger amplitudes. Hence a fixed collimator is designed to capture particles outside thebeam footprint on the PBW . The collimator will be designed for a power of 25 kW , although lower powersare expected.

• ESS project is ramping up!

– TDR being finalized

– Local organization is growing (and will

continue to grow)

– Expect to formally enter construction phase

next year.

• Baseline diagnostics suite defined. Many

diagnostics systems planned

– Some particular challenges include target

monitoring, bunch length and noninvasive

profile and halo

• Expect many more papers at coming IBICs…

Summary

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ESS Accelerator Divison (+guests), December 2011

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