362
L. Camilleri
TPC modules each containing 17,000 tons (10,000 tons fiducial volume) of liquid
argon. The construction of the first module will follow the APA, CPA concept being
tested in SBND, the so-called single-phase (liquid) approach. Its TPC dimensions
are 12 m high, 14.5 m wide and 58 m along the beam. Three rows of APAs will
be interleaved with 2 rows of CPAs, all oriented parallel to the beam. The APACPA horizontal separation, or drift length, will be 3.6 m, necessitating a 180 KV
high voltage system for a 500 V/cm drift field. Each row of APAs consists of 25
vertically stacked pairs. Each row of pairs of facing APA-CPA is surrounded by a
field cage. An APA consists of 4 wire planes separated by 4.76 mm with biases of
−655 V, −365 V, 0 V and +860 V and orientation of 0 ◦ , +35.7 ◦ , −35.7 ◦ and 0 ◦
respectively. The wire separation is 4.7 mm. The TPC data is continuously digitized
at 2 MHz by cold ADCs, serialized and transferred out of the cryostat on 12,000 high
speed links per 10 kton module. They are received by Reconfigurable Computing
Elements (RCEs) that buffer the raw data, zero-suppress it and pass it on to the
trigger. While the zero-suppressed data is kept for non-beam physics, a second pass
collects the full data set in regions of interest selected by the trigger. The photon
detector system consists of light guides (2.2 m long, 83 mm wide and 6 mm thick)
coated with TPB. The UV scintillation light impacting on the surface is re-emitted
inside the bar at 430 nm and internally reflected in the guide to reach 12 SensL
Cseries 6 mm 2 SiPMs. Ten such devices are mounted on each APA.
The second module will introduce a novel concept, the dual-phase approach first
studied in [79] and tested as described in [80], in which the drifting electrons exit the
liquid and are amplified in gaseous argon above the liquid. The concept is illustrated
in Fig. 8.13 depicting the design of the dual phase prototype, ProtoDUNE-DP [81],
currently under test at CERN. The DUNE dual phase module will consist of a
12 m wide, 12 m high and 60 m long homogeneous volume TPC. The electrons drift
vertically over a maximum of 12 m in the 500 V/cm field provided by a segmented
cathode at the bottom, the anode readout at the top and 60 stacked horizontal
rectangular field rings. The reduction of the number of drift electrons reaching the
wires due to absorption over the long drift space is compensated by the amplification
in the gas. A 2 kV/cm field between a grid located just below the surface of the liquid
and the Large Electron Multipliers (LEMs) charge amplification devices, causes the
electrons to be extracted. The LEMs consist of a 1 mm thick printed circuit board
with a micro-pattern of holes through its thickness and with one electrode on the
top and one on the bottom surfaces. A 3 kV potential difference between the two
electrodes results in a high field in each hole and the amplification of electrons
entering them by about an order of magnitude through an avalanche process. The
charge is collected in a two-dimensional x, y readout plane above the LEMs.
The technology of subsequent modules will depend on the performance of the
single phase and double phase prototypes currently being built and tested at the
CERN neutrino platform. DUNE also plans to use a near detector located close to
the Fermilab neutrino source.
The addition of a magnetic field to a liquid argon detector would greatly enhance
its capabilities. This has been tested [90] with an 11 L chamber placed in a 0.55 T
magnetic field and the drifting properties were found to be preserved. However
L. Camilleri
TPC modules each containing 17,000 tons (10,000 tons fiducial volume) of liquid
argon. The construction of the first module will follow the APA, CPA concept being
tested in SBND, the so-called single-phase (liquid) approach. Its TPC dimensions
are 12 m high, 14.5 m wide and 58 m along the beam. Three rows of APAs will
be interleaved with 2 rows of CPAs, all oriented parallel to the beam. The APACPA horizontal separation, or drift length, will be 3.6 m, necessitating a 180 KV
high voltage system for a 500 V/cm drift field. Each row of APAs consists of 25
vertically stacked pairs. Each row of pairs of facing APA-CPA is surrounded by a
field cage. An APA consists of 4 wire planes separated by 4.76 mm with biases of
−655 V, −365 V, 0 V and +860 V and orientation of 0 ◦ , +35.7 ◦ , −35.7 ◦ and 0 ◦
respectively. The wire separation is 4.7 mm. The TPC data is continuously digitized
at 2 MHz by cold ADCs, serialized and transferred out of the cryostat on 12,000 high
speed links per 10 kton module. They are received by Reconfigurable Computing
Elements (RCEs) that buffer the raw data, zero-suppress it and pass it on to the
trigger. While the zero-suppressed data is kept for non-beam physics, a second pass
collects the full data set in regions of interest selected by the trigger. The photon
detector system consists of light guides (2.2 m long, 83 mm wide and 6 mm thick)
coated with TPB. The UV scintillation light impacting on the surface is re-emitted
inside the bar at 430 nm and internally reflected in the guide to reach 12 SensL
Cseries 6 mm 2 SiPMs. Ten such devices are mounted on each APA.
The second module will introduce a novel concept, the dual-phase approach first
studied in [79] and tested as described in [80], in which the drifting electrons exit the
liquid and are amplified in gaseous argon above the liquid. The concept is illustrated
in Fig. 8.13 depicting the design of the dual phase prototype, ProtoDUNE-DP [81],
currently under test at CERN. The DUNE dual phase module will consist of a
12 m wide, 12 m high and 60 m long homogeneous volume TPC. The electrons drift
vertically over a maximum of 12 m in the 500 V/cm field provided by a segmented
cathode at the bottom, the anode readout at the top and 60 stacked horizontal
rectangular field rings. The reduction of the number of drift electrons reaching the
wires due to absorption over the long drift space is compensated by the amplification
in the gas. A 2 kV/cm field between a grid located just below the surface of the liquid
and the Large Electron Multipliers (LEMs) charge amplification devices, causes the
electrons to be extracted. The LEMs consist of a 1 mm thick printed circuit board
with a micro-pattern of holes through its thickness and with one electrode on the
top and one on the bottom surfaces. A 3 kV potential difference between the two
electrodes results in a high field in each hole and the amplification of electrons
entering them by about an order of magnitude through an avalanche process. The
charge is collected in a two-dimensional x, y readout plane above the LEMs.
The technology of subsequent modules will depend on the performance of the
single phase and double phase prototypes currently being built and tested at the
CERN neutrino platform. DUNE also plans to use a near detector located close to
the Fermilab neutrino source.
The addition of a magnetic field to a liquid argon detector would greatly enhance
its capabilities. This has been tested [90] with an 11 L chamber placed in a 0.55 T
magnetic field and the drifting properties were found to be preserved. However