Although the H0 can be identified unambiguously using a constrained fit to the unique topology characteristics of the H0 to Sigma-minus Proton decay, redundant particle identification will be provided by detecting the neutron from the subsequent Sigma-minus decay. Previous neutron detectors have achieved the necessary degree of spatial resolution by using narrow bars of scintillator whose width corresponded to the necessary granularity. Meanwhile constraints on efficiency and energy resolution were accomplished by incorporating several layers of scintillator into the detector in the direction of the expected neutron trajectory. An efficient neutron detector with good energy and angular resolution of this type becomes cost prohibitive when the price of the associated channels of electronics is included. This "three dimensional sensitivity" problem has been solved in a more cost effective way by the Catania group using a cylindrical detector geometry and employing multiple elliptical coordinates (MECS) as described in NIM A311 (1992) 280. Using MECS, it can be shown that the time that a particle impacts on a disc can be decoupled from the incident position on that disk. Thus using a series of disks, each disk becomes as simple as a rectangular strip but with an additional bidimensional sensitivity. This bidimensional sensitivity can be utilized to achieve the necessary spatial resolution without requiring the inordinate number of electronics channels needed in a bar-type detector with comparable resolution.
The Multi-functional Neutron Spectrometer (MUFFINS) consists of 30 coaxial disks of NE102A scintillator 3cm thick and 100cm in diameter spaced at 6.5cm intervals. This segmentation enables the MUFFINS detector to measure large neutron multiplicities. Each disk is viewed by six Hamamatsu R1398 PMTs located symmetrically around its edge. One output from each PMT is routed to an LRS 1881 ADC while a second is discriminated and sent to an LRS 1872 TDC. Even though the energy spectra and angular correlations of the neutrons are obtained by using TDC data, the ADC data is also important as it served to correct the TDC data for the slewing effects in the leading edge discriminators. The MUFFINS detector was previously used in a projectile fragmentation experiment at the LBL BEVALAC where it had a timing resolution of sigma=55ps. This timing resolution is in good agreement with the results of simulations. The intrinsic efficiency of each disk is typically 3.2%, which corresponds to a total intrinsic efficiency of 60% for neutrons with 300 < K.E. < 1000MeV. The efficiency was determined by comparing simulated output pulses, produced in GEANT for neutron interactions in MUFFINS, to the outputs observed experimentally using 1 GeV/c alpha particles.
