Versatile high flux backscattering spectrometer

Guide hall nº1, cold neutron guide H112

beam size at sample

30 x 30 mm2  (smaller for BATS t.b.d.)

Sample environment

cryofurnace (50 mm); max. sample diameter 48 mm

1.8 K - 560 K

cryostat (70 mm); max. sample diameter 68 mm

1.5 K - 320K


300 - 1300 K

vacbox 70mm - highly variable housing with outer dimension of orange cryostat with narrow tail; various vacuum tight connectors and feed through adaptable for your needs (to be prepared in time with an instrument responsible)

no temperature control foreseen yet, but possible near RT

no windows to secondary spectrometer which is typically in vacuum (ONLY if no risk of sample leakage! breaking & re-pumping of vacuum 1-2 hours) or otionally in air.



IN16B is on H112

  • efficient optics with ballistic neutron guide
  • two main configurations:
    • 'high flux' (HF) at guide end position or
    • 'low background' (LB) at guide side position
  • band width selection with selector and additional PG(002) deflector in LB configuration
  • flux gain through Phase Space Transformation (PST) chopper
  • more solid angle by new taller analysers
  • wider dynamic range through new Doppler linear motor drive and PST
  • lower background through background chopper and vacuum housing
  • secondary spectrometer can be operated alternatively without vacuum
  • several Doppler velocity profiles (sine, constant velocity)

change over times for configurations:

Change-over times between different configurations are long and if possible will be scheduled for a full or half cycles only. As an example the change from HF to LB configuration or back including alignment needs several days and the change between different monochromator/analyser configurations including alignment needs about 2 days.


standard: PSD multidetector array (16 tubes with vertical position sensitivity) + 2 3He counters + 1 monitor
alternatively: up to 8 3He single counters and no PSD
For diffraction: PSD's (in progress)

Instrument configurations



 standard E-resolutionhigh E-resolutionaccess to high Q with high E-resolutionbest E-resolution

wide E-transfer range


Si111Si111 polishedSi311

(first prototype commissioning 2017; to be continued end 2018)

chopper cascade & selector
(commissioning ongoing)

incident wavelength (Å)


dlambda/lambda ~12%

incident energy (meV) 

flux at the sample (n/cm2/s)
@ 58 MW

HF: 6.0 105 
LB: 8.7 104

t.b.d.HF: 1.2e5t.b.d., but sensibly lower than Si(111)



Si(111):  small angle & arc analysers of old IN16 type; 6 new tall Large Angle Analysers (LAAs)Si(111) polished:  small angle & arc analysers + only 3 old IN16 type LAAs (half height ±19°)Si(311): NO small angle & NO arc analysers; only 6 old IN16 type LAAs (half height ±19°)

~ 0.3 m2 test analyser

Si(111) or Si(311)

energy resolution (μeV)

∼0.75∼0.30 (~0.5 SANS)∼ 2.0reached ~ 75 neV in first commissioning March 2017

~ 1.5 - 8

energy transfer (μeV)


~ ± 250 / ±70 / -850...1000
Si(111) / Si(111) high rep. rate / Si(311)

Q-range (Å-1)

0.1 - 1.80.1 - 1.80.7 - 3.5t.b.d.

~ 0.2 - 1.8


high flux (HF) standard position

NEW: choose chopper ratio 1:1 for 'high flux' or 2:1 for 'high signal-to-noise' (HSNR-mode)

low background position (LB)  commissioned

available only if well justified (consider HSNR instead)

in HF position

monochromator now available

in HF position

be aware of Bragg contaminations from sample holder and cryostats

be aware of low flux

foresee delay in scheduling as accepted experiments need to be grouped into one cycle

German Verbundforschungs-project of FAU-Erlangen & ILL - financed by the German ministry BMBF

(July 2013 - July 2019)

commissioning of a reduced surface analyser and monochromator done in cycle 171

prototyping - not yet aimed for user operation

German Verbundforschungs-project of FAU-Erlangen & ILL - financed by the German ministry BMBF

(July 2013 - July 2019)

in user operation