Status of POST and Dome A Status of POST and Dome A

FTS SystemFTS System

Yao Yao QijunQijun ((yqj@mwlab.pmo.ac.cnyqj@mwlab.pmo.ac.cn))

Millimeter & SubMillimeter & Sub--millimeter Laboratorymillimeter Laboratory

Purple Mountain Observatory, CASPurple Mountain Observatory, CAS

The POSTThe POST--POPOrtablertable SSubub--millimeter millimeter

TTelescope (introduction)elescope (introduction)►►300mm off300mm off--axis parabolic, 8axis parabolic, 8’’ beam width beam width

@500GHz@500GHz

►►AzAz--EL driving by Harmonic DriveEL driving by Harmonic Drive®® gear and gear and

AC servo motorAC servo motor

►►SIS heterodyne receiver with 2SIS heterodyne receiver with 2--bits 500MHz bits 500MHz

autocorrelation spectrum analyzerautocorrelation spectrum analyzer

►►100mW 4K close100mW 4K close--cycle cooler with 1.2kW cycle cooler with 1.2kW

single phase 100V ACsingle phase 100V AC

The POST: system layoutThe POST: system layout

Tsys < 200K

Better stability

due to less

Josephson effect

High Tc relaxed

cooling requirement

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

(cooperated with NICT, Japan)

The POST: 0.5THz NbN SIS Mixer1st Astronomical observation ever made with an NbN SIS mixer(2008)

The POST: The POST: Receiver Module UpgradeReceiver Module Upgrade

�Mixer block and

Lens aligned by in-axis

mount hole;

�Cooled LNA is

installed close to mixer

to reduce the port

reflection;

�Good thermo-contact

by spring wash locked

back cover

The POST: The POST: LO Module modificationLO Module modification

►►4545°°LO plate LO plate

rotation to give a rotation to give a

inline polarization inline polarization

matching;matching;

►►More space for More space for

tuning knob means tuning knob means

a more easy a more easy

adjustingadjusting

The POST: The POST: Receiver System AssemblingReceiver System Assembling

�LO coupled

through 25um

Kapton film beam-

splitter

�Cold unit directly

mounted on 4K

cold head

The POST: Site survey at Tibet (2008)

The POST: 230GHz FFO+SIS

integrated receiver

►Demonstration of

FFO+SIS single

chip heterodyne

receiver

►Cooperation

between IREE

Russian and

PMO China

FTS: Dome A site survey on THzFTS: Dome A site survey on THz

�Why Dome A for THz:High altitude~4080m; Low temperature ~ High altitude~4080m; Low temperature ~ --6060℃℃ on on

average average �� lowest PWV become possiblelowest PWV become possible

�Challenge to face up��Low ambient temperature Low ambient temperature �� special designspecial design

��~1year unattended operation ~1year unattended operation �� high reliabilityhigh reliability

��LN2 unavailable LN2 unavailable �� precise precise calibrationcalibration

��RT detectors RT detectors �� limited sensitivitylimited sensitivity (high stability)(high stability)

－ Why and How?

Design of the FTS System－ System Specs

ModeMode Rapid scanRapid scan

Freq. RangeFreq. Range 0.750.75--15THz (15THz (LB: 0.75LB: 0.75--3.5THz, HB: 3.53.5THz, HB: 3.5--

15THz15THz))

Freq. ResolutionFreq. Resolution <10GHz<10GHz

Beam ApertureBeam Aperture >75mm>75mm

DLATGS NEPDLATGS NEP ~10~10--1010W/HzW/Hz0.50.5

Time/SpectrumTime/Spectrum 10mins10mins

MPI VolumeMPI Volume 0.7mx0.7mx0.3m0.7mx0.7mx0.3m

PowerPower <200W<200W

LowLow--bandband HighHigh--bandband

Freq Range (THz)Freq Range (THz) 0.5~3.50.5~3.5 3.5~153.5~15

Resolution (GHz)Resolution (GHz) 1010 1010

Optics EfficiencyOptics Efficiency 0.10.1 0.10.1

Beam Diameter Beam Diameter

(cm)(cm) 7.57.5 7.57.5

Throughput Throughput

(cm(cm22sr)sr)0.7920.792 0.1850.185

Detector Area Detector Area

(cm(cm22))0.1260.126 0.0290.029

Detector NEP Detector NEP

(W/Hz(W/Hz0.50.5))3.5e3.5e--1010 1.7e1.7e--1010

Parameters for Calculation

LB

HB

Based on DLATGS (RT) Based on DLATGS (RT)

detectors to achieve S/N>10detectors to achieve S/N>10

FTS:Estimation of Sensitivity

Design of the FTS System－ Optics Calculation for MPI

MPI optics

Zemax

Simulation

The FTS scanning benchThe FTS scanning bench- built by BlueSky

FTS system testing in Lab.

no tipping mechanism

calibrator & snow

cleaning structure

integrated

tilted window + brush

prevent snow on window

air sealed HDPE pipe

window ensure < 20W

heat dispersion

driver & oil specially

chosen for reliability (-

40℃/-90℃)

Design of the FTS System－ “Mailbox” Subsystem

FTS: Working status at Dome A

0 2000 4000 6000 8000 10000 12000 14000 16000 18000 200000.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

RAW

Freq(GHz)

01det1.cal

01det1.sky

0 1000 2000 3000 4000 50000.0000

0.0025

0.0050

0.0075

0.0100

RAW

Freq

01det2.sky

01det2.cal

Low band (0.5~3.5THz) 5 minutes scan

spectrum, Feb. 1, 2010. Tamb:-40℃

High band (3.5~15THz) 5 minutes scan

spectrum, Feb. 1, 2010. Tamb:-40℃

ConclusionConclusion

►►A compact 500GHz cooled receiver A compact 500GHz cooled receiver module proved to be a successful designmodule proved to be a successful design

►►THz opacity at Yangbajing site (4300m) THz opacity at Yangbajing site (4300m) has been fist measuredhas been fist measured

►►THz FTS system have been successfully THz FTS system have been successfully deployed on Dome A and working deployed on Dome A and working smoothlysmoothly