Injection Septum Chamber

Introduction: Injection septum chamber is installed in the first long straight section (LS-1) of INDUS-2 joining the  Transport Line-3 to the INDUS-2 ring. This  houses both 19° thick & 2° thin septum magnets  for injection of the electron beam at 700 MeV from booster synchrotron to INDUS-2. It is a multi-port cylindrical chamber with an internal diameter 450 mm and 1400 mm length. There are 19 ports of various sizes for different purposes. It is an ultra high vacuum chamber with massive gas load from laminations of septum magnets. Operating pressure inside the chamber is 2x10-9 mbar.

Design: Design requirements of this chamber include UHV compatibility, in-vacuum radial movement of septum magnets from atmospheric side, fixed and floating saddle supports for taking care of thermal expansion during baking, Rf-shielding for minimization of beam impedance, alignment and diagnostics features etc. Detailed engineering design is based on ASME pressure vessel code section-VIII, Division-I. Material of construction for this chamber is non-magnetic austenitic Stainless Steel AISI316L. Various activities involved in material inspection were visual, radiography, chemical analysis and Ultrasonography. Large end demountable flanges of 580 mm OD have been designed based on leak tightness criterion of < 2 x 10-10 std cc/sec. An important sub-system of this chamber is UHV compatible septum magnets base trolley with stainless steel spherical ball transfer units. These ball transfer units facilitate multidirectional rolling action with least coefficient of friction. These ball transfer units also simultaneously used for alignment of septum magnets. UHV compatible diaphragm bellow sealed linear motion feed-throughs of 25 mm stroke length are installed for providing movement to this trolley from atmospheric side. Al-alloy 6063-T6 dummy chamber with the same vacuum chamber (of INDUS-2) profile is installed inside the main chamber for minimizing the impedance to the wall current. This chamber also separates stored beam area (good field region) from high outgassing load from laminations of septum magnets. This helps in achieving longer  beam-life-time. Be-Cu finger contacts are installed at the end of this dummy chamber for continuity of the profile at these cross sections. Helium leak testing of the chamber has been done after fabrication and leak tightness found is < 2X10-10 std cc/sec of He. Photograph of the chamber without end blank flanges are shown below.

Injection Septum Chamber (INDUS-2)