A new Precision Measurement of the Neutron Electric Dipole Moment (EDM)
EDM Proposal PDF-file, version 28.04.2003
1ILL, Institut Laue-Langevin, 6 rue Jules Horowitz, 38042 Grenoble, France
2Ioffe Physical Technical Institute, Russian Academy of Science,
Politechnicheskaya 26, St. Petersburg, 194021, Russia
3Jagellonian University, 30059 Cracow, Poland
4LPC, Laboratoire de Physique Corpusculaire, Caen, France
5PNPI, St. Petersburg Nuclear Physics Institute, Gatchina, 188300, Russia
6PSI, Paul-Scherrer-Institut, 5232 Villigen, Switzerland
Physikalisches Institut, Philosophenweg 12
D-69120 Heidelberg, Germany
8Université de Fribourg, Chemin de Museé 3, CH-1700 Fribourg,
9Vavilov State Optical Institute, St. Petersburg, 199034, Russia
Short Description of the Experimental Program
We propose to perform a new precision measurement of the neutron electric dipole
moment (EDM) with an accuracy of
2 . 10-28ecm, an improvement by a
factor 100 over the currently most precise experiments. We will ultimately use the intense
source of ultra-cold neutrons (UCN) under construction at PSI.
We propose to build a new EDM spectrometer consisting of a set of
four double chambers with opposite electric fields, parallel or anti-parallel
to the magnetic field in each chamber, respectively, which will be adapted to handle
a high density of UCN in order to obtain the proposed accuracy.
In a first step, we intend to build a prototype EDM apparatus, the so-called Version I
or mini EDM spectrometer, with a total UCN storage volume of 24dm3 and to
neutron EDM at the UCN facility of
the Institute Laue-Langevin (ILL) in Grenoble. Due to the available UCN density
at ILL, the potential for an improvement over current experiments
is a factor of 3 already, and we hope to reach an
1 . 10-26ecm.
In a second step, after
the construction of the new PSI UCN facility, the sensitivity of this measurement
can be improved further by one order of magnitude with the mini EDM spectrometer,
to reach an accuracy of
1 . 10-27ecm.
Finally, increasing the
active volume of the EDM spectrometer by a factor 10 (Version II) or more in order to fully
adapt the spectrometer to the available UCN density or integral number of neutrons
at the PSI source, the EDM of the neutron can be measured with an accuracy
of about 2 . 10-28ecm.
We will use an EDM spectrometer based on the Ramsey resonance method.
It consists of a fourfold double-chamber setup which offers an increased
sensitivity to the neutron EDM. The fourfold double chamber setup reduces the background
originating from homogeneous as well as inhomogeneous magnetic field fluctuations.
The magnetic field will be measured and the
resonance frequency stabilized with a set of
16 Cs-magnetometers of very high sensitivity arranged around the neutron traps.
The four double chambers are
interspaced and surrounded
by 5 chambers with no electric field, serving as neutron magnetometers.
With this setup and a combined analysis of the 13 independent
resonance frequency shifts from the 4 double chambers and the five
neutron magnetometers we are able to simultaneously
measure the EDM and control systematic false effects.