[Neutron] effect of thickness on HOPG reflectivity for thermal neutrons

[Sax Mason]

Dear All,
Does anyone know of measured curves of
neutron reflectivity vs. crystal thickness
for pyrolytic graphite as used for neutron monochromators for thermal 
neutrons (e.g. ZYA quality HOPG).

Is there an optimum thickness for maximum flux of e.g. 2.4 Angstrom neutrons ?

Even unpublished results would be of interest.
Regards
Sax Mason

-- 

Sax A. Mason,  Institut Laue-Langevin (6 rue Jules Horowitz)  BP 156, 
38042 Grenoble Cedex 9, France
Tel: +33 476 207 067 (office) (d19: ...233, sec: ...226) Fax: +33476 
207 648 (or ...483 906)
e- mailto:mason at ill.fr   ill web: http://www.ill.fr/  d19: 
http://www.ill.fr/YellowBook/D19/help/index.html