Table 2.

Specifications and anticipated performance of the disk chopper spectrometer. Sets of three quantities within braces refer to the three resolution modes of operation of the instrument, {low, medium, high}, respectively

Specifications
Beam height at guide exit:				100 mm
Beam width at guide exit:				{30 mm, 15 mm, 5 mm}
Disk chopper details:
Outside radius:				290 mm
Maximum operating speed:				333 Hz (20,000 rpm)
Maximum tip velocity:				607 m/s
Pulsing chopper slot widths:				{12°, 6.5°, 2.6°}
Monochromating chopper slot widths:				{8°, 3.5°, 1.35°}
Order removal chopper slot widths:				20°, 18°
Frame removal chopper slot width:				20°
Sample-Detector distance:				4 m
Anticipated maximum scattering angle:				140°
Detectors (rectangular cross-section, 3He-filled)
Fill pressure:				0.6 MPa
Width:				−32 mm
Thickness:				~10 mm
Active length:				400 mm
Arrangement:				3 banks
Approximate incident wavelength range:				0.2 < λ0 < 1.5 nm
Approximate incident energy range:				20 > E0 > 0.36 mcV
Corresponding elastic Q range:				0.5 < Q < 60 nm−1
Anticipated performance (assuming a chopper speed of 20,000 rpm)
Fluence rate on sample			(λ0 = 0.2 nm):	{45, 10, 2} × 106 n/m2/s
“	“	“	(λ0 = 0.4 nm):	{450, 100, 20} × 106 n/m2/s
“	“	“	(λ0=0.6 nm):	{220, 50, 10} × 106 n/m2/s
“	“	“	(λ0 = 0.8 nm):	{100, 20, 5} × 106 n/m2/s
Elastic energy resolution			(λ0 = 0.2 nm):	{1300, 650, 270} u,eV
“	“	“	(λ0=0.4 nm):	{160, 80, 35} µeV
“	“	“	(λ0 = 0.6 nm):	{50, 25, 12} µeV
“	“	“	(λ0 = 0.8 nm):	{21, 11, 6} µeV