Optimal shape of a cold-neutron triple-axis spectrometer

Lefmann, Kim; Filges, Uwe; Treue, F.; Kirkensgard, J. J. K.; Plesner, Bitten; Hansen, Kurt Schaldemose; Klenø, Kaspar Hewitt

doi:10.1016/j.nima.2010.06.273

Cited by 8 publications

(5 citation statements)

References 17 publications

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“…For instruments of 60 m and longer, and for the 40 m triple-axis instruments, we have employed elliptical guides for beam transport, since recent experiments and simulations has shown this design to be strongly superior over traditional curved guides 6,24 . For the values of guide reflectivities, we have everywhere used recent information from one supplier 25 .…”

Section: The Guide Systemsmentioning

confidence: 99%

“…The exact value of the exponent will clearly depend on the chosen instrument suite, but it is interesting to note firstly that the instrument performance scales more closely with the peak flux than with the time-average flux. Secondly, equation (6) predicts that the global instrument performance depends only on the time-average flux and duty cycle. If both are kept constant, e.g.…”

Section: Optimization Of the Full Instrument Suitementioning

confidence: 99%

“…The simulation results of the 15 individual instruments are available on-line 4 and are or will be published individually in more detailed articles [5][6][7][8][9][10][11][12] .…”

Section: Introductionmentioning

confidence: 99%

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Simulation of a suite of generic long-pulse neutron instruments to optimize the time structure of the European Spallation Source

Lefmann

Klenø

Birk

et al. 2013

Review of Scientific Instruments

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We here describe the result of simulations of 15 generic neutron instruments for the long-pulsed European Spallation Source (ESS). All instruments have been simulated for 20 different settings of the source time structure, corresponding to pulse lengths between 1 ms and 2 ms; and repetition frequencies between 10 Hz and 25 Hz. The relative change in performance with time structure is given for each instrument, and an unweighted average is calculated. The performance of the instrument suite is proportional to a) the peak flux and b) the duty cycle to a power of approx. 0.3. This information is an important input to determining the best accelerator parameters. In addition, we find that in our simple guide systems, most neutrons reaching the sample originate from the central 3-5 cm of the moderator. This result can be used as an input in later optimization of the moderator design. We discuss the relevance and validity of defining a single Figure-ofMerit for a full facility and compare with evaluations of the individual instrument classes.

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Section: The Guide Systemsmentioning

confidence: 99%

Section: Optimization Of the Full Instrument Suitementioning

confidence: 99%

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Simulation of a suite of generic long-pulse neutron instruments to optimize the time structure of the European Spallation Source

Lefmann

Klenø

Birk

et al. 2013

Review of Scientific Instruments

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“…To a first approximation, the curvature for the (002) planes is 1/R M . The final geometry of the curvature is the result of a McStas computer optimization, as described in [17]. …”

Section: Therein the Vertical Focusing Is Provided By A Circular Curmentioning

confidence: 99%

A Monte Carlo Simulation of Neutron Instrument Resolution Functions

et al. 2013

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In this paper we demonstrate that the Monte Carlo simulation package McStas is a useful tool, not only for instrument design, but also for resolution function calculation. It has been possible to determine analytically the 4 dimensional resolution function of both a direct geometry time of flight neutron spectrometer and a triple axis spectrometer. The obtained resolution functions are directly comparable to and in agreement with the Monte Carlo simulated results. These results are a step towards incorporating a 4 dimensional resolution function into data analysis. For each instrument we show an example of the resolution function calculated at a particluar point in (Q, ω) space.

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“…5 However as neutron spectroscopy moves towards smaller sample sizes, the natural collimation produced by the distance between, e.g., sample and analyser can become comparable to, or better than, the mosaicity of standard graphite analysers. It has been shown that relying on distance collimation instead of mosaicity and the conventional parallel beam approximation can lead to better performing monochromators 6 so it would be natural if the same was true for analysers. We will show that this is indeed the case and additionally demonstrate the opportunity to analyse several energy bands simultaneously with a single analyser.…”

Section: Introductionmentioning

confidence: 99%

Prismatic analyser concept for neutron spectrometers

Birk

Markó

Freeman

et al. 2014

Review of Scientific Instruments

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Articles you may be interested inThe new cold neutron chopper spectrometer at the Spallation Neutron Source: Design and performance Rev. Sci. Instrum. 82, 085108 (2011) Developments in modern neutron spectroscopy have led to typical sample sizes decreasing from few cm to several mm in diameter samples. We demonstrate how small samples together with the right choice of analyser and detector components makes distance collimation an important concept in crystal analyser spectrometers. We further show that this opens new possibilities where neutrons with different energies are reflected by the same analyser but counted in different detectors, thus improving both energy resolution and total count rate compared to conventional spectrometers. The technique can readily be combined with advanced focussing geometries and with multiplexing instrument designs. We present a combination of simulations and data showing three different energies simultaneously reflected from one analyser. Experiments were performed on a cold triple axis instrument and on a prototype inverse geometry Time-of-flight spectrometer installed at PSI, Switzerland, and shows excellent agreement with the predictions. Typical improvements will be 2.0 times finer resolution and a factor of 1.9 in flux gain compared to a focussing Rowland geometry, or of 3.3 times finer resolution and a factor of 2.4 in flux gain compared to a single flat analyser slab. © 2014 AIP Publishing LLC. [http://dx

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Optimal shape of a cold-neutron triple-axis spectrometer

Cited by 8 publications

References 17 publications

Simulation of a suite of generic long-pulse neutron instruments to optimize the time structure of the European Spallation Source

Simulation of a suite of generic long-pulse neutron instruments to optimize the time structure of the European Spallation Source

A Monte Carlo Simulation of Neutron Instrument Resolution Functions

Prismatic analyser concept for neutron spectrometers

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