Priya Arora

Note: Reliable and reusable ultrahigh vacuum optical viewports

We report a simple technique for the realization of ultrahigh vacuum optical viewports. The technique relies on using specially designed thin copper knife-edges and using a thin layer of Vacseal(®) on tip of the knife-edges between the optical flat and the ConFlat(®) (CF) flange. The design of the windows is such that it gives uniform pressure on the flat without breaking it. The assembled window is a complete unit, which can be mounted directly onto a CF flange of the vacuum chamber. It can be removed and reused without breaking the window seal. The design is reliable as more than a dozen such windows have survived several bake out and cooling cycles and have been leak tested up to 10(-11) Torr l/s level with a commercial Helium leak detector. The advantages of this technique are ease of assembly and leak proof sealing that survives multiple temperature cycling making the windows reliable and reusable.

Simple alignment technique for polarisation maintaining fibres.

We describe a simple technique for rapid alignment of input state of polarisation with respect to the preferred axis of polarisation maintaining fibres. In this technique a combination of a half-wave and a quarter-wave plate is used to turn the polarisation of incoming beam and to compensate for stress-induced perturbation of polarisation states in a laid-out fibre, respectively. The angular alignment technique is tested with temperature excursion on the fibre. The technique is easy to implement, affordable, and gives quick and accurate alignment.

Diagnosis of precocious puberty due to tuber cinereum hamartoma by clinicoradiologic correlation

We present a case of a 3 year male child who presented with precocious puberty. Endocrinological studies revealed increased LH and increased testosterone. Bone age was 8 years. MR Imaging showed hypothalamic mass isointense to brain parenchyma on T1-WI and hyperintense on T2-WI, without contrast enhancement. Typical clinical presentation, endocrinological studies and MRI features strongly favoured the diagnosis of tuber cinereum hamartoma. This case is presented to emphasize the importance of clinicoradiologic correlation in the diagnosis of precocious puberty due to tuber cinereum hamartoma.