Brussels, 2 February 2006 Next generation spallation sources: short and long pulses F. Mezei

Brussels, 2 February 2006

Next generation spallation sources:

short and long pulses

F. Mezei

ES 06-04

Energy balance / heat production is key for ultimate performance of high power sources

Pulsed spallation sources vs. fission reactors - 8 times less heat per neutron - order of magnitude better efficiency by pulses

Fusion is only 2x better in heat production vs. spallation, but extreme particle energy is a problem to stay

Pulsed spallation sources are the high flux neutron sources of choice for the foreseeable future with a potential of orders

of magnitude gain compared to today.

Future neutron sources

High power short pulses (by accelerator or storage rings): limited by shock wave damage / cavitation in target

~ 1s proton pulses poorly match the 10 – 300 s neutron moderator response time

Linear accelerators can produce the same energy per pulse in ~ 100 s pulses at much less damage & costs

Longer and more intense pulses (ms) are advantageous for cold and thermal neutron applications:> 1014 n/cm2/pulse compared to < 1013 for SNS

Pulsed spallation sources can provide at equal costs and less technical complexity much higher time average and higher

peak flux in long pulses than in short ones.

Note: rotating wheel targets might make possible to extend the power limits of the short pulse approach well beyond the “proven” limit of ~ 1 MW. Higher

costs and development needs!

Future neutron sources

Pulse length requirements by scientific needs:

Irradiation work:

Single (Q,) experiments (D3, TAS?): SANS, NSE: 2 – 4 ms

Reflectometry: 0.5 – 2 ms

Single Xtal diffraction: 100 – 500 s

Powder diffraction: 5 – 500 s

Cold neutron spectroscopy: 50 – 2000 s

Thermal neutron spectroscopy: 20 – 600 s

Hot neutron spectroscopy: 10 – 300 s

Electronvolt spectroscopy: 1 – 10 s

Backscattering spectroscopy: 10 – 100 s, …

Peak flux characterizes source performance for sufficiently long pulses to avoid intensity loss by excessive resolution

Shaping of ms long pulses feasible for > 95 % of cases

Scientific performance

Progress in source performance

0 1 2 3 4 5 6 7 8

1012

1013

1014

1015

1016

1017

ILL hot source ILL thermal source ILL cold source

SNS 1.4 MW, 60 Hz thermal moderator coupled cold moderator

Flu

x [n

/cm

2 /s/s

tr/Å

]

Wavelength [Å]

Lines: peak fluxes

Shaded area: scientific capabilities(except irradiation & single Q)

Staged approach in major accelerator projects: key to the success of high energy physics community

Criteria for a first stage: substantially lower costs, complexity and technical development needs

Possible first stages for ESS by ~ equal costs:a) 5 MW long pulse target stationb) ~1 MW short pulse target station

ESS staged realization

ESFRI Neutron WG Report. Expert group:

A. Furrer, C. Vettier, R. Cywinski, F. Mulder, H. Zabel, W.I.F. David,

H. Jobic, M. Latroche, J. Comenero, D. Richter, A. Arbe, F. Barocchi, R. McGreevy, F. Mezei,

G. Fragneto, D. Myles, P. Timmins, R.Rinaldi, B. Winkler, S.

Redfern, H. Rauch.

ESFRI scenarios

0 1 2 3 4 5 6 7 8

1012

1013

1014

1015

1016

1017



ESS LPTS 5 MW, 16.7 Hz, 2 ms bispectral thermal - cold

Flu

x [n

/cm

2 /s/s

tr/Å

]

Wavelength [Å]

Progress in source performance

ESS LPTS advantages:

Higher cold peak fluxMore often „sufficient“ pulse lengthAdjustable resolutionCleaner line shape

ESFRI scenarios

ESFRI scenarios

Operating costs: long pulse operation shows good efficiency in power consumption

Staged approach to major accelerator projects: key to the success of high energy physics community

Criteria for a first stage: substantially lower costs, complexity and technical development needs

Possible stages for ESS by ~ equal costs:a) 5 MW long pulse target stationb) ~1 MW short pulse target station

Scientific opportunities much higher for a)

The 5 MW long pulse target station as first step is the only scientifically meaningful option for a staged realization of ESS.



UK Technical report (Carpenter et. al) endorses ESS assessment


UK Technical report (Carpenter et. al) endorses ESS assessment

Sufficient experience available by TOF instruments and developments on continuous sources (spectroscopy, reflectometry, diffraction,…)

1017

1015

Pulse shaping technique for diffraction and inverted geometry spectroscopy at long pulse sources

Multiplexing chopper system (with phase slewing to source)

Wavelength Frame Multiplication

0 5 10 150

5

10

15

Pulse shaping chopper

Wavelength band chopper #1

Dis

tanc

e [m

]

Time [ms]

A fancy multidisc velocity selector (RISP)

ESS study on pulse shaping

0 1 2 3 4 5 6 7 8

1012

1013

1014

1015

1016

1017



Optimized LPTS 15 MW, 16.7 Hz, 2 ms bispectral thermal-cold hot moderator

Flu

x [n

/cm

2 /s/s

tr/Å

]

Wavelength [Å]

Optimized LPTS up-grade: next generation

Next generation

Current projects (SNS, J-PARC)

Today (ILL, ISIS)

ESS SAC workshop, 0ct 2002 for ESFRI report

Source strength benchmarked against SNS (1.4 MW)

0,0

5,0

10,0

15,0

20,0

25,0

30,0

35,0

40,0

45,0

1 2 3 4 5 6 7 8 9 10

ISIS II

ISIS / ILL

50Hz1MW

LPTS (5 MW)

Full ESS

LPTS (15 MW)

Cold ChopperHigh ResolutionBackscattering

High ResolutionPowder

High Intensityreflect.

High IntensitySANS

High ResolutionProtein

EngineeringDiffractometer

Variable,Cold Chopper

High ResolutionNSE

SNS

Thermal Chopper

Optimized spallation sources: orders of magnitude enhanced research opportunities in condensed matter. Largest gains vs. current projects by long pulse approach.

Conclusion

5 MW SPTS

Brussels, 2 February 2006 Next generation spallation sources: short and long pulses F. Mezei

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