MANU2

Collaboration:

INFN and University Genova

Location of the experiment: Genova

National Responsible: F. Gatti (Ge)

Home page of the Experiment: http://www.ge.infn.it/~opisso/vitale.html

1. Goal of the experiment.

The experiment aims to perform the total energy disperse beta-spectroscopy of 187Re by means of cryogenic micro-calorimeters working at 100 mK, with an energy resolution competitive to the electron-impulse beta spectroscopy of the Tritium experiments. Check of the anomalies at the end-point and a model independent measurement of neutrino mass are the main physics goals. Behind the aims, the study of the Beta Environmental Fine Structure for application to the matter science is of primary interest.

2.

Activities during 2001

The experiment needs micro-calorimetric detectors with a target energy resolution (FWHM) of 5 eV (Milestone 1) and with a broad band SQUID read-out (Milestone 2). The measurements must be done in a refurbished dilution refrigerator (Milestone 3). The work on the development of high-resolution micro-calorimeters accumulated a delay because of the reorganization of the group after the death of Prof S. Vitale. In the fall 2001 we recovered part of this delay. A big step toward a high resolution micro-calorimeter has been done: a 25 eV FWHM micro-calorimeter with excellent thermal and electrical characteristics has been obtained. The broad band SQUID electronics is fully tested. The Oxford Instruments will deliver the new refrigerator’s insert and the ancillary parts in February 14, 2002 (0% Milestone 3).

Achievements of energy resolution better than 5 eV | 30-04-2001 | 70%
Prototype of a wide bandwidth SQUID electronics | 31-08-2001 | 100%
Detector engineering and cryostat refurbishment | 31-12-2001 | 0

Milestones 2002:

Building, installation and test of 1/3 of the required detector | 30-06-2002
Tuning-up of the data acquisition system | 30-10-2002
End of detector's installation and test, start of data taking | 31-12-2002

3. INFN contribution to the experiment in terms of manpower and financial

Manpower: 10 researchers (4.1 FTE), 2 technician and support from the mechanics and the electronics workshops of INFN-Genova

Budget for the year 2002:175.5 kEuro

4. Publications in refereed journals (in 2001): 3

5. Number of conference talks (in 2001): 5

6. Number of undergraduate and doctoral thesis:

2 undergraduates

2 Ph.D.

7. Leadership role in the experiment.

F. Gatti is the spokesman

8. Innovative instruments

The experiment developed unique thermal detectors with superconducting absorber with high Z (=75) and high density (=21) capable to reach energy resolution about 1 order of magnitude better than commonly available solid-state detectors. Applications to X-ray spectroscopy with same spectroscopic resolution of dispersive Bragg crystal are foreseen. We developed high performances TES sensors: we obtained one of the best thermometric responsivity (7500-10000 1/K) among the groups working on cryogenic detectors. We have successfully examined the perspective of possible application of the BEFS effect for the study of microcrystalline structure in situations where EXAFS is not suited.

9. Competing experiments

No other groups developed superconducting rhenium detector. No other groups have achieved the sensitivity to observe the beta environmental fine structure of beta decay (BEFS). Our group first proposed the use of Rhenium for neutrino mass measurements, and observed for the first time the beta spectrum with cryogenic detectors. The competing experiment is Mi-Beta that started the data taking after MANU was completed. Mi-Beta makes use of absorber made of dielectric crystal of silver perrhenate. The resolution of Mi-Beta is better than our old detectors, with equivalent or lower mass of rhenium-187. Presently, MANU-2 is developing detectors with same performances. Better performances are predicted in the near future.

10. International committee which has reviewed the experiment

The INFN National Committee II annually reviews MANU2.