ALMA/45m/ASTE Users Meeting 2022

2022/12/21 via Hybrid (MTK and Zoom)

New capabilities for future Cycles
Masumi Shimojo (NAOJ/NINS)
as behalf of the collaborators of developing new capabilities of ALMA

Note:

This presentation is preliminary information. In this talk, I will present thecandidates for the new capabilities offered in near future Cycles.
The pre-announcement for Cycle 10 will be released by the ALMA observatory
in January, and the actual new capabilities for Cycle10 will be announced.

2

The candidates for the new capabilities in near future Cycles

In this talk, I will brieﬂy introduce the following candidates, except for ACASPEC and Band1.

• Performance improvement(PI cannot select them. The OT or/and Observatory applies them to suitable projects.)• ACA Spectrometer (ACASPEC): new spectrometer for the TP-array ➜ Later talk (Ishii-san)• Band-to-Band (B2B) phase calibration for 7m-array and compact 12m-array• 4x4 bit mode of the Base-Line Correlator (BLC) for FDM• New observing modes for new science• Band1 : new receivers for 35‒50 GHz ➜ The talk series of Band1 (Nagai-san, Yen-san, and Zavala-san)• Spectral scan with the TP array• VLBI: ﬂexible tuning for spectral line VLBI, and new Band (Band1)• Solar polarization observations with Band3 and 12m-array (Stokes-V)3

<<Performance Improvement>>

Band-to-Band (B2B) phase calibration

Expanding to the 7m-array and compact 12m-array• When higher-band projects are scheduled, the ALMA observatory searches the calibrators near the scientiﬁctargets with the observing Bands. However, there is sometimes no suitable phase calibrator near the target.
Since Cycle 9, if there is a suitable phase calibrator near the target for lower bands, we observe the phasecalibrator with lower band, obtain the Gain, and apply the processed gain table to the higher-band science
data (the Band-to-Band[B2B] phase calibration transfer).

• The function have been used since Cycle 9 only for the projects using large 12m-array conﬁgurations (C-8,9, 10).

• In near future Cycles, the treatment might be applied to the observations with the 7m-array and compact
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CHAPTER 10. CALIBRATION AND CALIBRATION STRATEGIES

12m-array conﬁgurations (< C-8).

Mode typeNon-harmonic
Harmonic
Non-harmonic
Harmonic
Harmonic
Harmonic
Harmonic
Harmonic
Harmonic

Band Pairs
B7 - B3
B7 - B3
B8 - B4
B8 - B4
B8 - B6
B9 - B4
B9 - B6
B10 - B5
B10 - B7High Freq. LO1 range
282.9 - 324.0 GHz
324.0 - 365.0 GHz
393.0 - 399.0 GHz
399.0 - 465.0 GHz
465.0 - 492.0 GHz
610.2 - 697.5 GHz
697.5 - 711.9 GHz
794.7 - 848.7 GHz
848.7 - 942.3 GHz

Table 10.1: Band pairings used for B2B phase calibration.
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From the Cycle 9 Technical handbook

<<Performance Improvement>>

4x4 bit mode of the BaseLine Correlator (BLC) for FDM

Reducing the sensitivity loss by the quantization in BLC
5.1. THE 64-INPUT CORRELATOR

59

3bits per a sample

Correlator station electronics

4 GHz Digitizer
4 GHz Digitizer
4 GHz Digitizer

DATA
Transmitter
DATA
Transmitter

Digitizes analog signals andapplies ultra fine delay

4bit2bits per a sample
32-parallel outputs x 2-bits
per sample x 2-polarizaitons
Antenna 63

32-parallel outputs x 2-bits
per sample x 2-polarizaitons
Antenna 0DATA
ReceiverTunable Filter Bank Card

DATAReceiver

Tunable Filter Bank Card

DATA
ReceiverTunable Filter Bank Card

DATAReceiver

Tunable Filter Bank Card

Three optic
carriers

Tunable Filter Bank Card

Tunable Filter Bank Card

Tunable Filter Bank Card

Tunable Filter Bank Card
Fine delay andselects bandwidth

One quadrant to process
one baseband, two polarizations

Station Card

Station Card

Station Card

FDM mode• TFB can output the data with 4 bits per sample.
bits data → 4x4 bit mode.

• Due to 4x4 bit mode, the sensitivity loss by theLTA-addertree

Intra-quadrant
results cross bar
and real timecomputerinterface

Real timecomputersystem

quantization can be reduced.

• The mode would be applied to the FDM data
mainly with narrow bandwidth.

4 PCB
Vertical drive to correlator matrix after Correlator array,

4 bits per a sample

2bits per a sample
Figure 5.2: Overview diagram of the ALMA digitizers, data transmission system and 64-input Correlator(Escoﬃer et al. 2007, A&A 462, 801). The digitized data from the individual BBs are transferred to theTunable Filter Banks (TFBs) and station cards (top right) for the parallelization and processing required oneach antenna data stream. The correlator array (lower half) produces auto-correlations on the main diagonal
and cross-correlations elsewhere in the correlator matrix. The correlations are then integrated in the Long-Term
Accumulators (LTAs, lower right).

5.1.2

Input: 2 bits, Output: 2bits→ 2x2 bit mode.

Bulk delay, re-orders
and packetizes samples

Correlator array(one of 4 quadrants in system shown)Long term
accumulator(LTA)• Current BLC operation mode:• BLC can treat 4 bits input data and can output 4Station Card

Correlator baseline electronics

before BLC,

Horizontal drive to correlator matrix

before BLC,

Three opticcarriers

Plane 31

4 GHz Digitizer

Plane 24 GHz Digitizer

DATATransmitter

12:1 Optical Splitter

4 GHz Digitizer

Plane 1

4 GHz Digitizer

Plane 0

POL 2

DATA
Transmitter
12:1 Optical Combiner

4 GHz Digitizer

with 4bits per a sample

3bit → 2bits

At antenna
POL 1

TFB can output the data

TFB reduce bit

32-parallel outputs x 2-bits
per sample x 2-polarizaitonsat the ADC of each antenna,

From the Cycle 9 Technical handbook• In near future Cycles, the mode might be applied

to the FDM with the Dual Polarization (XX and YY).

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<< New observing modes for new science >>Spectral scan with the TP array• In the spectral scan mode, we can change local frequencies (LO1)

ﬁve times in one observation to cover the required frequency range.

• The mode can be used only for interferometric observations (12marray and 7m-array).

• In near future Cycles, we might be able to use the mode for the TParray.

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<< New observing modes for new science >>Flexible tuning for spectral line VLBI, and new Band
• Current VLBI observations with ALMA (Band3, 6, and 7)• The observing frequencies cannot be changed in each Band (see the table).
• Since Cycle 9, spectral-line VLBI observations with Band3 have been oﬀered. The mode does not have thefunction to tune the LO1 frequency ﬂexibly. The mode is that phasing of the array is computed using a narrowspectral window within the ﬁxed frequency range of the spectrum window(spw)#1 (using the LO1 frequency in thetable). So, the mode is suited for observations mainly of Galactic SiO masers.

• For the furture cycles, the following VLBI capabilities are investigated& Band1• VLBI continuum and spectral line observations with Band1.
• In the Spectral Line VLBI mode with Band1, 3, 6, and 7,• 1 spw can be used for VLBI with Band1 & 3• 4 spws can be used for VLBI with Band6 & 7.

Band1

41.16843.16845.16847.124• However, how many spws are usable for VLBI depends on the data obtained with other observatories.
• The center frequency of each spw is tunable (The LO1 frequency is also tunable).
• The bandwidth of each spw is ﬁxed to 1875 MHz.
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<< New observing modes for new science >>Solar polarization observation with Band3 and 12m-array

To measure chromospheric magnetic ﬁeld strength above sunspots• The linear polarized emission from the Sun is predicted as negligible small in microwave and millimeterwave range, and no one succeeded in detecting linear polarization signal.

• The circular polarized mm-wave emission (Stokes-V) above a sunspot is predicted (< a few %). Thepolarization is caused by the opacity diﬀerence of X- and O-mode. From the Stokes-V data, we would
be able to estimate chromospheric magnetic ﬁeld strengths.

• Full polarization solar observations only with Band3+12m-array might be oﬀered in near future Cycles.

?

Stokes-V Band38

End

This presentation is preliminary information. In this talk, I presented thecandidates for the new capabilities offered in near future Cycles.
The pre-announcement for Cycle 10 will be released by the ALMA observatory
in January, and the actual new capabilities for Cycle10 will be announced.

10