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In this paper, we describe the development of a new L-band (1.4 GHz)Cryogenic Phased Array Feed (PAF) system, referred to as the GBT2 array.Results from initial measurements made with the GBT2 array are also presented.The PAF was developed for the Green Bank Telescope (GBT) as part of the FocalL-band Array for the GBT (FLAG) project. During the first stage of thedevelopment work (Phase I), a prototype cryogenic 19 element dual-polarizedarray with "Kite" dipole elements was developed and tested on the GBT. Themeasured system temperature over efficiency ($T_{sys}/\eta$) ratio for the boresight beam of the Kite array was 45.5 K at 1.55 GHz. The off-boresight$T_{sys}/\eta$ shows an increase by 13 K at an offset equal to the half powerbeam width (7$^{'}$.2 at 1.7 GHz). Our measurements indicate that theoff-boresight degradation and field-of-view (FoV) limitation of the Kite arrayis simply due to the fixed array size. To increase the FoV, a new 19-elementGBT2 array with larger array spacing was developed during FLAG Phase II. Thefrequency response of the array was optimized from 1.2 to 1.6 GHz. A systemwith larger cryostat, new low noise amplifiers (LNAs), down-conversion anddigitization close to the front end, unformatted digital transmission overfiber, ROACH II based polyphase filter banks (PFBs) with bandwidth 150 MHz anda data acquisition system that records voltage samples from one of the PFBchannels were all developed. The data presented here is processed off-line. Thereceiver temperature measured with the new system is 17 K at 1.4 GHz, animprovement $>$ 8 K over the previous Kite array. Measurements with the GBT2array on the telescope are in progress. A real time 150 MHz beamformer is alsobeing developed as part of an NSF-funded collaboration between NRAO/GBO/BYU \&West Virginia University (Beamformer Project) to support science observations.

A Highly-Sensitive Cryogenic Phased Array Feed for the Green Bank Telescope