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The scintillator bar measures 200 x 10 x 10 cm3. The attached light guides measure 6.25" in length tapering to a 2" diameter cylinder after 5 in. An aluminum flange is mounted at the base of the cylinder with the end extending 1" beyond the flange. The scintillator material is BC-408 with a bulk attentuation length greater than 3.8 m. The light guide material is a UVA acrylic plastic known as BC-802. The plastic scintillator bars and light guides are manufactured by Saint-Gobain.

The plastic scintillator bars as delivered by Saint-Gobain.

Cross section of the PMT/lightguide assembly.

Phototube Assemblies

Photonis X2262B 12 stage 51 mm (2") photomultiplier tubes are used in the detector. These tubes provide a nominal gain of 6.0 x 107 and an anode pulse rise time of 2 ns.

Testing and Assembly Manual

The manual for testing and assembling the detector bars is avaliable in pdf format.

Simulation of Light Propagation

Paul DeYoung and his student P.J. VanWylen from Hope College did a simulation of the light propagation in the detector bar. They found that the light attenuation deviates from an exponential curve.

Support Table

The MoNA modules are arranged in an array and held in position by a support assembly. The The support table design is a construction of steel I-beams with a flat deck. The deck is covered with a layer of plywood/rubber. Rails to the left and right of the deck accomodate vertical stands. A set of four stands is mounted on the inner pair of rails. These stands prevent the stacked detector bars from toppling off the front or the rear of the table. They hold the detector at the light guides, outside of the active area. The outer pair of rails will take vertical stands to which the steel converters can be mounted. In addition, cable trays are located on the sides of the detector array.

support assembly for MoNA

An isometric view of the complete MoNA array. In this view, the detectors are arranged in a 16 x 9 layer format. Steel converters are not shown, however the mounting posts are in place. The cable trays can be placed as needed. The view also shows a spreader bar that enables us to lift the complete detector and move it with the overhead crane.

The MoNA project was made possible by funding from the National Science Foundation under grants
PHY-0110253, PHY-0132367, PHY-0132405, PHY-0132434, PHY-0132438,
PHY-0132507, PHY-0132532, PHY-0132567, PHY-0132641, and PHY-0132725.

Copyright © 2006 MoNA Collaboration