ICALEPCS2011 - List of Authors (Mana, G.)

Paper

Title

Page

Measuring Angle with Pico Meter Resolution

1014

P. Mutti, M. Jentschel, T. Mary, F. Rey
ILL, Grenoble, France
G. Mana, E. Massa
INRIM, Turin, Italy

The kilogram is the only remaining fundamental unit within the SI system that is defined in terms of a material artefact (a PtIr cylinder kept in Paris). Therefore, one of the major tasks of modern metrology is the redefinition of the kilogram on the basis of a natural quantity or of a fundamental constant. However, any kilogram redefinition must approach a 10^-8 relative accuracy in its practical realization. A joint research project amongst the major metrology institutes in Europe has proposed the redefinition of the kilogram based on the mass of the ¹²C atom. The goal can be achieved by counting in a first step the number of atoms in a macroscopic weighable object and, in a second step, by weighing the atom by means of measuring its Compton frequency vC. It is in the second step of the procedure, where the ILL is playing a fundamental role with GAMS, the high-resolution γ-ray spectrometer. Energies of the γ-rays emitted in the decay of the capture state to the ground state of a daughter nucleus after a neutron capture reaction can be measured with high precision. In order to match the high demand in angle measurement accuracy, a new optical interferometer with 10 picorad resolution and linearity over a total measurement range of 15° and high stability of about 0.1 nrad/hour has been developed. To drive the interferometer, a new FPGA based electronics for the heterodyne frequency generation and for real time phase measurement and axis control has been realized. The basic concepts of the FPGA implementation will be revised.

Poster WEPMS019 [6.051 MB]

Paper	Title	Page
WEPMS019	Measuring Angle with Pico Meter Resolution	1014
	P. Mutti, M. Jentschel, T. Mary, F. Rey ILL, Grenoble, France G. Mana, E. Massa INRIM, Turin, Italy
	The kilogram is the only remaining fundamental unit within the SI system that is defined in terms of a material artefact (a PtIr cylinder kept in Paris). Therefore, one of the major tasks of modern metrology is the redefinition of the kilogram on the basis of a natural quantity or of a fundamental constant. However, any kilogram redefinition must approach a 10^-8 relative accuracy in its practical realization. A joint research project amongst the major metrology institutes in Europe has proposed the redefinition of the kilogram based on the mass of the ¹²C atom. The goal can be achieved by counting in a first step the number of atoms in a macroscopic weighable object and, in a second step, by weighing the atom by means of measuring its Compton frequency vC. It is in the second step of the procedure, where the ILL is playing a fundamental role with GAMS, the high-resolution γ-ray spectrometer. Energies of the γ-rays emitted in the decay of the capture state to the ground state of a daughter nucleus after a neutron capture reaction can be measured with high precision. In order to match the high demand in angle measurement accuracy, a new optical interferometer with 10 picorad resolution and linearity over a total measurement range of 15° and high stability of about 0.1 nrad/hour has been developed. To drive the interferometer, a new FPGA based electronics for the heterodyne frequency generation and for real time phase measurement and axis control has been realized. The basic concepts of the FPGA implementation will be revised.
	Poster WEPMS019 [6.051 MB]