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)

S2

1 (

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)

S1

1 (

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)

Td

ipo

le

(K)

Achievable Tsys?

PAF Workshop Provo, UT May 3-5, 2010 10

Contributor Noise

Receiver 9

Dipole Losses 2

Mutual Coupling 2

Spillover 5

CMB and Atm 4

Total 22 K

Next

PAF Workshop Provo, UT May 3-5, 2010 11

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