Cryogenic PAF DevelopmentProgress Report

PAF WorkshopMay 3-5, 2010

Provo, UTRoger Norrod

Cryogenic PAF

PAF Workshop Provo, UT May 2010 2

• BYU/NRAO targeting noise and efficiency competitive with best single-beam receivers. i.e. 18K, 70% at L-band.

• At Green Bank, construction of cryostat for

19 element L-band PAF underway.

PAF Cryostat

PAF Workshop Provo, UT May 3-5 2010 3

With blank-off covers for leak checkApril 27

Model Drawing24 X 21 X 8 in.61 X 53 X 20 cm.

Dual LNA and Thermal Transition

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Pair of two-channel LNAs with integrated low-loss coaxial lines for transition from 15 to 300K, vacuum seal, and antenna base interface.

LNA based on: S. Weinreb, J. Bardin, H. Mani, G. Jones, “Matched wideband low-noise amplifiers for radio astronomy”, Rev. of Sci. Instr., vol. 80, 044702, 2009.

NXP SiGe transistors.Surface mount components.Thin-wall SS tubular coax.Quartz beads for vacuum seal and center conductor heat sink.

Est. input coax heat load 150 mW / chan.Bias power 17 mW / chan.

14 of 20 assembled, 8 tested cold.

LNA Measured Performance

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1300 1400 1500 1600 1700 18005

7

9

11

13

15

Dual LNA Noise8 Amps, 16 Channels Shown

Frequency (MHz)

Trx

(K)

1000 1200 1400 1600 1800 200035

37

39

41

43

45

Dual LNA Gain8 Amps, 16 Channels Shown

Frequency (MHz)

S21

(dB)

Noise Y-factor measured with LN2 cold load at room temperature SMA connector.

LNA Measured Performance

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1000 1200 1400 1600 1800 2000-20

-15

-10

-5

0

Dual LNA S118 Amps, 16 Channels Shown

Frequency (MHz)

S11

(dB)

LNA Measured Performance

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1300 1400 1500 1600 1700 18000

10

20

30

40

50

60

70

80

90

100

SN6-Y Noise vs. Physical Temperature

15K 31K 41K 51K 61K71K 81K 91K 108K 194K302K

Frequency (MHz)

Trx

(K)

0 100 200 3000

10

20

30

40

50

60

70

80

90

SN6-Y Noise vs. Physical TempAt 1660 MHz

LNA Body Temperature (K)

Trx

(K)

Dipole Ohmic Losses

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Sky noise tests Nov-Dec 2009 to determine dipole noise contribution. Measured on Ciao room-temp amps (~35K).

Dipole Ohmic Losses

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1. Measured LNA/Rx with coaxial hot/cold load.

2. Attached dipole and measured using ambient load and sky.

3. Corrected for scatter, galactic plane, etc. (Tsky = 7.5K)

1300 1400 1500 1600 1700 1800-5

-4

-3

-2

-1

0

1

2

3

4

5

Fat Dipole Noise Contribution17 Dec 09

Tdipole on SN102 Tdipole on SN124

Frequency (MHz)

Tdip

ole

(K)

Achievable Tsys?

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Contributor Noise

Receiver 9

Dipole Losses 2

Mutual Coupling 2

Spillover 5

CMB and Atm 4

Total 22 K

Next

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• Install LNA/TT assemblies.• Cooldown, measure cooling capacity.• Mount in FEB.• Sky noise tests.• Antenna (20m) tests.