Docstoc

Development of THz Superconducting Mixers _amp; Dome A THz Project

Document Sample
Development of THz Superconducting Mixers _amp; Dome  A THz Project Powered By Docstoc
					  Development of THz
Superconducting Mixers &
  Dome A THz Project



Sheng-Cai Shi, Qi-Jun Yao, and Ji Yang
    Purple Mountain Observatory
    Chinese Academy of Sciences
        OUTLINE

        Introduction

THz Superconducting Detectors

FTS for Site Testing at Dome A

         Conclusion
       Why do THz Astronomy?

 electronics    Size~λ             hν~kBT             photonics
                                            dust emission

  ~50% photon energy after
         CMB
 cold (10K@1THz) objects in
         formation
                                            Ivison et al. 2000
                                            Ivison et al. 2000
  early distant objects (dust                        obscured active
                                             heavilyCSO Spectrum of Orion
 reemission and red shift)                   galactic nuclei


deep inside (seeing through)
of objects, optically thin @
            THz
                Credit: Chris Walker
 rich molecular rotation lines
& fine-structure atomic lines
    Superconducting Mixers for THz
        ALMA-ACA, artist’s rendition




   Capability of large facilities depend mostly
   upon micron/nano-scaled detecting devices                                           ∆Tmin = kTsys   Bτ

    0.1THz     fgap~1.4THz                                                                             10~100 THz
                      Photon
                     Assisted
                                        Εk
                                                                         radiation
                    Tunneling                quasi

SIS Mixers                                   electron
                                             s
                                                                                                  HEB Mixers
                                                                     e            S
                        εF
                    ΝS(E)
                               ∆
                               ∆
                                        0
                                             ∆   εF          N   e
                                                                                           N
                   density
                                                                         e   ph
                                             ∆   ΝS(E)
                   of states
                                                 density     e
                                                 of states                        ph
                                                                         L
                    quas
                    i
                                   V0
                                                             Substrate
                    hole
                    s                   Εk
    Development of THz
 Superconducting Detectors
    Superconducting SIS mixers for 13.7m
           telescope and POST
  Superconducting SIS mixers for SMA and
                 ALMA
 Superconducting HEB mixers for future THz
                 projects
Preliminary results with superconducting direct
                  detectors
3x3 Multibeam 2SB SIS Receiver
       for Delingha-14m
       corrugated
       horn

         2SB SIS
         mixers
         LO
         coupler

       HEMT LNA



         1st POST
         amplifier
         A 0.5THz NbN SIS Mixer
     1st Astronomical observation ever made with an NbN SIS mixer




POST 0.5THz NbN SIS mixer & Observed CO (J=4-3)



                                                     better stability
                                                      due to less
                                                   Josephson effect
                                                     relaxed cooling
                                                      requirement
                Development of Submm
                  SIS Mixers for SMA



credit: ASIAA/SAO




                    荷兰空
                    间所
      紫台-
      紫台
      IAA



                          哈佛
     加洲理工                 CfA
                         [
                   ]z H G yc n e u q er F
015   094   074      054          034       014   093   073
                                                              0
                                                              05
                                                              001
                                                              051 T
                                                                  S
                                                                  S
                                                              002 B
                                                                  [
                                                                  K
                                                              052 ]
                  ) % 0 8( c e p S
                   )y n a( c e p S                            003
                    1L O P B SL
                   1L O P B S U                               053
                                                              004
                  Purple Mountain Observatory, NAOC, China
                  National Astronomical Observatory of Japan
             385–500 GHz Cartridge
                 ALMA Band 8
Joint Development of SIS Mixers for
          ALMA Band 10

 with Nb SIS
junctions & Al
    wiring




0.85THz NbN SIS
     mixer
                         with all-NbN SIS
                             junctions
Development of 1.4THz
   NbN SIS Mixers




              Vgap = 5.4mV
              Rn = 23.8ohm
              Jc = 20kA/cm2
              f0 = 1.22THz
THz Superconducting HEB Mixers
               measured HEB sample
                                                                  hyper-hemispherical Lens
                                                                    with Parylene coating




                                        chopper               Comparison of noise
                                                                 performance
vacuum
window                                            reflector
                                  µ
                                36µm
                                Mylar
                        lens
                                           77 K load

                   wire grid

Gunn+Multiplier/
  BWO/Laser                    measurement setup
Development of 5.2THz HEB Mixers
in Collaboration with SRON/TUDelft
                                      0.20


                                      0.15




                       Current (mA)
                                      0.10


                                      0.05


                                      0.00
                                             0         2            4                6          8          10
                                                                   Voltage (mV)
                                                   0.8 1.0   1.4        1.6
                                      5000
                                                                               2.0
                                      4500

                                      4000




                   DSB Trec (K)
                                      3500                                    1.8

                                      3000
                                                 0.6         1.2
                                      2500

                                      2000

                                      1500
                                         0.01      0.02      0.03             0.04       0.05       0.06
                                                                   Current (mA)
    Preliminary Results with
Superconducting Direct Detectors

                                                                         A Compact THz
                                                                              FTS
                                                                          bandwidth:
                                                                          bandwidth:
                                                                           0.1~5THz
                                                                         resolution:
                                                                         resolution:
                                                                             <5GHz

       -6
  7.0x10

       -6
  6.0x10

       -6
  5.0x10

       -6
  4.0x10

       -6
  3.0x10

       -6
  2.0x10

       -6
  1.0x10


      0.0
         300   350   400   450   500   550   600

 Response for a 0.5THz NbN SIS mixer               NEPs of an HEB vs Temperature
              Good THz Sites on the Earth

SMA, Mauna Kea, Hawaii
Altitude: 4080m
Average Temp: ~0℃
                ℃




                                                   SPT, South Pole
                                                   Altitude: 2835m
ALMA, Chajnantor, Chile                       Average Temp: -49℃ ℃
Altitude: 5100m
Average Temp: -2℃
                ℃
                          credit: C. Walker
   Dome A: the Best THz Site on
            the Earth?

                      credit: C. Walker                   SMA (25%)


                             Dome A @661GHz



                                                         ALMA (win.
                                                         median)
                                                         CCAT
                                                         DomeC
    Altitude: 4093m
      Tmin: -83℃
               ℃
Distance from Zhongshan:
                       :
                                      Photo credit: Zhou Xu & Zhu Zhengxi
         1300km                                      (2008)
      Design of the FTS System
             - Basic Requirements
  unattended operation

  long-duration (~1yr)

   Largest bandwidth for FTSs ever used for
site testing

  no LN2 used     no low-temp calibration

  Cryogenically cooled detectors cannot be
used   limited detection sensitivity
Design of the FTS System
   - Schematic of the System



                    “Mailbox”


                      MPI
                    Subsystem



    Control & DAQ
      Subsystem
         Design of the FTS System
                   - System Specs
Mode                 Rapid scan
Freq. Range          0.75-15THz (LB: 0.75-3.5THz, HB: 3.5-
                     15THz)

Freq. Resolution     <10GHz

Beam Aperture        >75mm

DLATGS NEP           ~10-10W/Hz0.5

Time/Spectrum        10mins

MPI Volume           0.7mx0.7mx0.3m

Power                <300W
           Design of the FTS System
                         - “Mailbox” Subsystem
                                     no tipping for simplicity
                brush                 calibration load (LT) & snow
     LT load                       cleaning structure integrated

window1                              tilted window plus brush adopted
                                   for cleaning snow on the window
               window2               two windows and thermal isolation
PLATO                              adopted less than 20W heat
Roof Top            MPI            dispersion
                    Subsystem
                                     HDPE or LDPE window adopted
                                   for large bandwidth
                                    LT-load radiation temp precisely
                                   measured
                                     driver & oil specially chosen for
                                   reliability
Control/DAQ System & Software




 Diagram of Control/DAQ Subsystem
                    Estimation of Sensitivity
                                           LB
    Parameters for Calculation
                    Low-band   High-band

Freq Range (THz)     0.5~3.5    3.5~15

Resolution (GHz)       10         10

Optics Efficiency      0.1        0.1
Beam Diameter
    (cm)               7.5        7.5
                                           HB
  Throughput
    (cm2sr)
                     0.792       0.185
 Detector Area
     (cm2)
                     0.126       0.029

 Detector NEP
   (W/Hz0.5)
                     3.5e-10    1.7e-10


S/N>10 achievable with DLATGS
       (RT) detectors
Timeline for FTS Development
  End of 2008: Proposal & concept design
  2009/1-3: System design and contract
negotiation
  2009/4: Contracted with QMC/Bluesky for MPI
and DLATGS detectors
  2009/4-7: Subsystem design & starting
construction
  2009/8: System integration & lab testing
  2009/9: further testing, training, preparing
installation/operation manual
  2009/10: deploying to Dome A
                Conclusion
   A 100GHz Multibeam 2SB SIS receiver is under
                  development
  A 0.5THz NbN SIS mixer has been successfully
  developed and demonstrated for 1st time for
           astronomical observations
     Major contribution to the development of
submm SIS mixers for SMA (ASIAA) and ALMA (NAOJ)
   Superconducting HEB mixers beyond 1THz have
    been developed for future THz projects
   A THz FTS is under construction and will be
          deployed at Dome A in 2009
                   Acknowledgment
The work presented here was supported in part by the NSFC under Grant No.
   10673033, 10621303, 10811140090 and 10778602, by CAS under the
International Collaboration Program GJHZ0617, and by the China Exchange
Programme, which is the framework of the scientific cooperation between the
     Netherlands and P.R. China, and is executed by KNAW and CAS.
Contributions in superconducting detectors from W.L. Shan, J. Li, W. Zhang,
    W. Miao, Y. Ren, X.S. Cao, K.M. Zhou, J.Q. Zhong, and Z.Q. Li are
                                appreciated.
  Dome A FTS is a collaboration project between PMO1 & CfA2. Major
  members include Sheng-Cai Shi1, S. Paine2, Q.J. Yao1, X.X. Li1, X.G.
 Zhang1, Z.H. Lin1, H. Matsuo3, J. Yang1, and Q.Z. Zhang2. We appreciate
 valuable discussions with Ken Wood of QMC, D. Naylor and B. Gom of
     Bluesky, M. Ashley and J. Story of Plato team, and CCAA team.

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:10
posted:5/8/2011
language:
pages:25