The NOE Calorimeter design

The guideline for our design is to keep the sampling fraction as high as possible while using a moderate SCIFI density and, at the same time, two instrumented views, to allow a full $E_{t}$ measurement. A homogeneus sampling of the shower can be achieved by spreading the SCIFI's over the full calorimeter volume.

A possible choice to fulfill these requirements is made of calorimetric bars obtained using SCIFI embedded in iron ore (Crossed Fiber Bars - CFB). Such absorber is inexpensive and shows a low radioactivity background. We chose a calorimetric cell structure of $5 \times 4.4$ cm$^{2}$ with 33 2 mm diameter SCIFI embedded, resulting in a fiber/iron ore ratio in volume of $\simeq 1 \div 20$. The resulting sampling fraction is not so far from the SCIFI calorimeters quoted in the Introduction. Infact the higher fiber/Pb ratio in volume of the CHORUS, E864 and H1 calorimeters (1:4, 1:4.55 and 1:3.4 respectively) is roughly compensated by the factor 3.3 between the iron ore density ($\rho$=3.5 g/$cm^{3}$) with respect to the Pb one. The full calorimeter structure can be easily obtained by combining single bars, thus resulting in an easy mechanical construction.

An evolution of the previous layout is made of crossed SCIFI planes (Crossed Fiber Planes - CFP) interleaved with a thin absorber of iron sheets ($\simeq$5 mm). Each fiber plane consists of self-supporting slabs made of recycled plastic. The average density is roughly unchanged with respect to the previous CFB option. The main advantage of this design is the possibility of magnetizing the iron slabs, thus allowing a muon charge and momentum measurement in the same detector. Fig. shows the two calorimeter options.

As a first step we have studied the calorimeter performance building and testing a calorimeter prototype based on CFB option, in order to simplify and to speed up the construction, while keeping the same fiber density and sampling fraction of the CFP option.