Diamond as a carbon standard for MAN bremsstrahlung

[JohnF]

I am looking to make a new MAN standard mount. I have in the past used graphite to pin the curves at the low Z end of the plots. I am wondering what people think about diamond as a reference material (it will be carbon coated). In my 3 decades of EPMA I have heard whispers and comments about diamond not being that "good" as a reference material, due, if I recall correctly, to it's strong(?) insulator character [yes, many of the minerals we use are also insulators but the epma community has generally ignored that issue, except for Cazaux and Jbara]. What say those folks reading this email?? Is diamond "good enough" to generate a representative bremsstrahlung for Z>6??