Planar Edgeless Silicon Detectors Planar Edgeless Silicon Detectors for the for the TOTEMTOTEM Experiment Experiment

1.E-09

1.E-06

1.E-03

3.4 3.9 4.4 4.9

1/T, 1e3/K

Cur

rent

, A

(294K) (256K) (227K) (204K)

Gennaro Ruggiero, CERN, PH Department, CH-1211 Geneva 23, Switzerlande-mail: gennaro.ruggiero@cern.ch

On behalf of the

TOTEMTOTEM Collaboration

Gennaro Ruggiero, CERN, PH Department, CH-1211 Geneva 23, Switzerlande-mail: gennaro.ruggiero@cern.ch

On behalf of the

TOTEMTOTEM Collaboration

……the proof!!!the proof!!!

The idea…The idea…

To measure the total cross-section of the LHC the To measure the total cross-section of the LHC the TOTEMTOTEM experiment will detect leading protons coming experiment will detect leading protons coming from the Interaction Point 5 (IP5)from the Interaction Point 5 (IP5)

The best choice for such detectors are silicon The best choice for such detectors are silicon microstrips planes placed orthogonally to the beam microstrips planes placed orthogonally to the beam axis. Nevertheless in standard fabrication these axis. Nevertheless in standard fabrication these devices present an insensitive edge of 1mm where devices present an insensitive edge of 1mm where termination structures are placed to improve their termination structures are placed to improve their breakdown performance. To reduce this dead region breakdown performance. To reduce this dead region the TOTEM collaboration has developed a the TOTEM collaboration has developed a new new approach for the realisation of devices with approach for the realisation of devices with insensitive edges of only 50insensitive edges of only 50m!!!m!!!

The leading proton detectors will be The leading proton detectors will be installed in special beam insertion, the installed in special beam insertion, the Roman PotsRoman Pots and will approach the 10 and will approach the 10 of the of the high intensity beam as close as possible.high intensity beam as close as possible.

The conceptual idea of the new approach is to apply The conceptual idea of the new approach is to apply the full detector bias across the detector chip cut and the full detector bias across the detector chip cut and collect the resulting leakage current on an outer ring, collect the resulting leakage current on an outer ring, which surrounds the active area and which is biased which surrounds the active area and which is biased at the same potential as the detecting strips. This ring at the same potential as the detecting strips. This ring is separated from the detector biasing electrode. is separated from the detector biasing electrode. Separating this ring from the bias ring strongly Separating this ring from the bias ring strongly reduces the influence of the current generated at reduces the influence of the current generated at detector edge on the active detector area. In contrast detector edge on the active detector area. In contrast with the other ring structures which provides voltage with the other ring structures which provides voltage termination, this structure terminates the current, and termination, this structure terminates the current, and therefore we have called it therefore we have called it Current Terminating Current Terminating StructureStructure..

First silicon detectors with this First silicon detectors with this CTSCTS produced produced in August 2003 (joined effort between the in August 2003 (joined effort between the TOTEM-CERN and Ioffe PTI- St.Petersburg/ TOTEM-CERN and Ioffe PTI- St.Petersburg/ RIMST Moscow).RIMST Moscow).

•Bulk Leakage Current not influenced by the Bulk Leakage Current not influenced by the Edge Edge Surface CurrentSurface Current (I (I

22 << << II11) at 300K) at 300K

•II1 1 does not decrease exponentially with the does not decrease exponentially with the

TemperatureTemperature

Terminating structure 40 Terminating structure 40 m wide m wide

Front Side Back Side

CMS TOB hybrid

Reference Detector (RD)

2 Test Detectors (TD)

Self-referencing module made of a board in G10 Self-referencing module made of a board in G10 laminated with kapton hosting a reference detector laminated with kapton hosting a reference detector (RD) and two test detectors (TD). All the detectors (RD) and two test detectors (TD). All the detectors readout with APV25 chips packed in the CMS TOB readout with APV25 chips packed in the CMS TOB hybridhybrid

Self-referencing module with Self-referencing module with detectors and readout electronicsdetectors and readout electronics

Test Beam Results (at 300 K)Test Beam Results (at 300 K)(Sept. ‘03, muon beam in X5 at CERN)(Sept. ‘03, muon beam in X5 at CERN)

RD

TD TD

TDTD

RD

Data from Test Beam: (1229±8)m

TDTDTDTD

Metrology:(1209±10)m

40 40 mmI2I1

+-

bias ring Al

p+

n+

cut edge Al

SiO2

n-type bulkp+

current terminating

ring

Thermo-Electric CharacterizationThermo-Electric Characterization

Roman Pot StationsRoman Pot Stations

I1

I2

reverse bias of 100Vreverse bias of 100V

The sensitivity at the edge of detectors with CTS has The sensitivity at the edge of detectors with CTS has been measured with a muon beam by checking been measured with a muon beam by checking coincident hits in two Test Detectors with CTS with the coincident hits in two Test Detectors with CTS with the cut edges, facing each other and being parallel, and in cut edges, facing each other and being parallel, and in a Reference Detector placed on their back with the a Reference Detector placed on their back with the strip direction parallel to the sensitive edges of the two strip direction parallel to the sensitive edges of the two TD’s. TD’s.

Due to the high spatial resolution of the RD Due to the high spatial resolution of the RD (strip pitch of 50 microns), the insensitive (strip pitch of 50 microns), the insensitive distance between the two TD’s can be distance between the two TD’s can be measured precisely and can be compared measured precisely and can be compared with the mechanical distance enabling a with the mechanical distance enabling a precise determination of the efficiency drop precise determination of the efficiency drop at the edges of the test detectorsat the edges of the test detectors

Cross-section of a Silicon detector with Current Cross-section of a Silicon detector with Current Terminating Structure and its biasing scheme.Terminating Structure and its biasing scheme.

Distribution of hits in the reference detector Distribution of hits in the reference detector in coincidence with hits in the two test in coincidence with hits in the two test detectors. Their fit is compared to the detectors. Their fit is compared to the beginning of the sensitive area of the two beginning of the sensitive area of the two TD’s (dashed red line).TD’s (dashed red line).

Detail of the edge of a microstrip silicon Detail of the edge of a microstrip silicon detector with Current Terminating Structure. detector with Current Terminating Structure. With this type of terminating structure the cut With this type of terminating structure the cut of the dice can be even just 40of the dice can be even just 40m away from m away from the end of the strips.the end of the strips.

New Development:New Development:Current Terminating StructureCurrent Terminating Structure

Excellent detector stability for biases Excellent detector stability for biases higher than 200V at room temperature.higher than 200V at room temperature.

Signal-to-noise distribution of the test detector at the Signal-to-noise distribution of the test detector at the edge as recorded by the reference detector at the end edge as recorded by the reference detector at the end of the strip (position 74) and 50 of the strip (position 74) and 50 m away (position m away (position 75 )75 )

The signal-to-noise performance of the Test Detectors as a function of the x-position as recorded by the Reference Detector have shown a uniform value around 22 until 50m away from the strips end. This suggests full efficiency up to this position. However, the S/N distributions at the edges show a slight decrease in the pulse height, indicating a loss in efficiency of 10-20 %.