INTRODUCTION
The tailpiece is the housing in which the target insert is placed.
It's shape is rougly a vertical cylinder 18 inches in length.

The main functions of the tailpiece are:
-Contain the liquid helium 1K bath created by the refrigerator 
-Allow beam passage and scattered particle exit through thin windows
-Provide a guide rail system to properly orient the target insert

The main requirements for any tailpiece design are:
-Attach to the circular flange at the bottom of the shell that
contains the refrigerator
-Provide contact with the refrigerator shell by means of an indium seal
-Remain helium leak tight and un-deformed with around 1.25 atmosphere
pressure on the inside and vacuum on the outside at a 1 K temperature
-Contain no magnetic materials
-Contain no material with unpaired/polarizable protons
-Consist of radiation-hard materials, particularly the beam windows

DESCRIPTION

General
Vertically, the tailpiece is divided into two sections.  The top
section provides the flange that connects to the refrigerator shell,
the indium sealing surface, and houses the guide rails that assure
that the insert is at the proper rotation.
The lower section contains the beam windows, and is sized to allow the
insert to travel vertically in order to place one of several targets
in the beam.

Windows
Three windows are needed: beam entry, beam/electron exit, and proton
exit.  It is important that the two beam windows be parallel and
separated by 3.4 cm.  The proton exit window ideally should be normal
to the beam windows and placed as close to the insert as possible, but
may be curved or positioned at a few mm away from its optimal position
as engineering considerations dictate.

Insert
The cross section of the part of the target insert that sees beam is