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Simulation of a suite of generic long-pulse neutron instruments to optimize the time structure of the European Spallation Source
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10.1063/1.4803167
/content/aip/journal/rsi/84/5/10.1063/1.4803167
http://aip.metastore.ingenta.com/content/aip/journal/rsi/84/5/10.1063/1.4803167

Figures

Image of FIG. 1.
FIG. 1.

Artists view of the ESS target/instrument buildings seen obliquely from above. Note that the long instruments are placed in a hall (foreground left) which is separated from the main target building (right). The accelerator is seen stretching into the background.

Image of FIG. 2.
FIG. 2.

(left) Sketch of the main elements of the cold chopper spectrometer. Picture is not to scale. (right) Time-of-flight diagram illustrating the selection of neutron pulses by choppers, with the spectrometer running in RRM mode with = 5.

Image of FIG. 3.
FIG. 3.

Simulated plots of the moderator surface showing the number of neutrons which reach the sample at the IN5-like chopper spectrometer. Top panel shows the situation with a 60 m guide (τ = 1 ms), while bottom panel shows the results for a 100 m guide (τ = 2 ms).

Image of FIG. 4.
FIG. 4.

(left) Sketch of the main elements of the long SANS instrument. Details are not to scale. (right) Time-of-flight diagram illustrating the selection of wavelength band by choppers, with the spectrometer running in the (20 + 20) m setting.

Image of FIG. 5.
FIG. 5.

Simulated plots of the moderator surface showing the number of neutrons which reach the sample for the 20 m SANS instrument. The results are valid for any time structure. (top) data for 2 m collimator-detector setting; (bottom) data for 20 m collimator-detector setting.

Image of FIG. 6.
FIG. 6.

Average Figure-of-Merit for the generic ESS instrument suite at different time structures, plotted as a function of the inverse source duty cycle, under the assumption of constant time-average flux. Diamonds, squares, crosses, and circles represent pulse lengths of 2.0, 1.5, 1.25, and 1.0 ms, respectively. The solid line is a fit to the power law (6) , as explained in the text.

Tables

Generic image for table
Table I.

Properties of 15 generic ESS instruments, suggested by the ESS-S SAG and the ESS SAC. denotes the length of the instrument for a pulse length of τ = 1 ms, while is the instrument length for τ = 2 ms, and β is the “Frascati exponent,” defined by (1) .

Generic image for table
Table II.

Relative Figure-of-Merit (FoM) values for the simulations of the IN5-like cold chopper spectrometer at ESS, under the assumption of constant time-average flux. Simulations are performed for 20 different settings of the time structure, (, τ). The RRM scheme is parametrized by , which indicates the number of possible monochromatic pulses at the sample per source pulse.

Generic image for table
Table III.

Relative Figure-of-Merit (FoM) values for the simulations of the long SANS instrument at ESS under the assumption of constant time-average flux. Simulations are performed for 20 different settings of the time structure, (, τ).

Generic image for table
Table IV.

Average relative Figure-of-Merit for the generic ESS instrument suite at different time structures, under the assumption of constant time-average flux.

Generic image for table
Table V.

Average relative Figure-of-Merit for the generic ESS instrument suite at different time structures, under the assumption of constant peak flux.

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/content/aip/journal/rsi/84/5/10.1063/1.4803167
2013-05-07
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Simulation of a suite of generic long-pulse neutron instruments to optimize the time structure of the European Spallation Source
http://aip.metastore.ingenta.com/content/aip/journal/rsi/84/5/10.1063/1.4803167
10.1063/1.4803167
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