Welcome to Gianluigi Casse’s home page
Here you can find summarised part of the silicon detector activity in the Physics Department of the University of Liverpool. You can also look to my personal page, by clicking here
Silicon detector studies
This page summarises the work done in the silicon detector laboratory of the HEP Group (University of Liverpool - Department of Physics)
Experiments I am involved
Atlas, LHCb, RD50. Some of the work I have performed in the framework of these experiments can be found below.
 Radiation tolerance of silicon detectors
The silicon detectors will provide the main tracking capability for the future experiments in high-energy physics. In most of these experiments they will have to withstand a harsh radiation environment. The survival of the detectors to the severe radiation fluences they will receive is a challenge for the detector technology. We are involved in the development of the sensors for several of the major experiments that will take place in CERN-LHC (ATLAS, LHCb) and FERMILAB (CDF). In this page I have collected several results concerning the study of silicon detectors mainly on the subject of their radiation hardness.

SCT ATLAS sensors page: a systematic study of the radiation behaviors of the sensors for the ATLAS tracker has been carried out for a few years. The Liverpool University was heavily involved in this program. A number of results obtained within this program is collected in the following section: pre and post irradiation characterisation of SCT ATLAS sensors.

Notes (*)   Irradiations were performed in November '98, with the 24 GeV/c CERN/PS proton beam. The cumulated fluence is 3 1014 cm-2.
(**) Irradiations were performed in April '99, with the 24 GeV/c CERN/PS proton beam. The cumulated fluence is 3 1014 cm-2.
(***) Irradiations were performed in July '99, with the 24 GeV/c CERN/PS proton beam. The cumulated fluence is 3 1014 cm-2.
(****) Irradiations were performed in November '99, with the 24 GeV/c CERN/PS proton beam. The cumulated fluence is 3 1014 cm-2.
The detectors were under 100 volts bias and were irradiated at -9 oC in a dry N2 atmosphere. All these irradiations have been performed by the University of Sheffield group and thanks, in particular, to C.M. Buttar, I. Dawson, C. Grigson, R.S. Harper.....

Performances of Hamamatsu (Ham.) and Micron (Mic.) ATLAS wedge detectors before and after irradiation (*)
Reverse current vs bias
Non irr. Ham. 98
Non irr. Ham. W12-37055 family
Non irr. Ham. SXX-37160 family (thin detectors)
Non irr. Mic. 98
Irradiated Ham. (*)
Irradiated Mic. 98  (*)
Irradiated Ham.  SXX-37160 (**) 		Backplane capacitance vs bias
Non irr. Mic.
Non irradiated Ham. 300 and 250 micron thick.
Irradiated (*) Micron : 1732-2-1, 1732-2-2 1733-2-1
Irradiated  (*): STX41618-11, STX41618-12. 		Interstrip capacitance
Non irr. Ham. W12
Non irr. Mic. 1733-2-2
Irr. Ham. STX41618-12, short strips  (*)
Irr. Ham. STX41618-12, long strips  (*)
Irr. Mic. 1732-2-1, short strip  (*)
Irr. Mic. 1732-2-2, short strip  (*)
Irr. Mic. 1732-2-2 long strip  (*) 		Noise vs bias for irradiated detectors
Micron (*) 1732-2-1
Micron (*) 1733-2-1
Micron (*) 1732-2-2
Hamamatsu (*)   STX41618-11
Hamamatsu (**) SXX -37160 family (thin detectors)
Strip integrity Irradiated (*) MICRON 1732-1-1, 1732-2-2, 1733-2-1
Irradiated (*) Hamamatsu STX41618-12
 Studies for CDF
Full depletion voltage vs operation time at various temperature Currents for operations at various temperature (fluence in neutron cm-2): Strip current (strip width = 50 micron, length = 15 cm, detector thickness = 300 micron)
Volume current
Total reverse current of Layer00 prototype detectors.
Interstrip capacitance of Layer00 prototype detectors: MSL 1721-24
Interstrip capacitance of new (08/99) Layer00 prototype detectors.
Comparison between Hamamatsu and SGS Thomson Layer00 detectors.
 Oxygen enrichment technique
I've conceived the high temperature diffusion technique to introduce high concentrations of oxygen into silicon wafers. This development was done in the frame of RD48 collaboration. It can be used for other fast diffusing element in silicon. You find here the description of this technique.
Also look in:  http://www.brunel.ac.uk/research/rose/rosetn.htm and in http://rd48.web.cern.ch/RD48/, Technical Reports page, ROSE/TN/99-1.
You can find further details in Chapter 5 and Appendix B of my PhD thesis.
 Results with oxygenated diodes .....
and some more with large area detectors .....

Can the oxygenation technique be used for the production of large area segmented detector? Firsts results with microstrip detectors processed by MICRON on 4" <100> silicon substrate oxygenated for 110 hours at 1100 oC. A standard silicon detector is used for control.
Preirradiation measurements:
I-V; Interstrip capacitance: oxygenated and control ; Strip vs backplane capacitance.
Measurements after irradiation (***):
I-V's: comparison between oxygenated and control. C-V's: comparison between oxygenated and control.
Intrstrip capacitance: oxygenated and control
Charge collection efficiency: comparison between MICRON microstrip (6x6 cm2) control un-oxygenated and
oxygenated detectors with laser (1064 nm) and source (106Ru) signals.
All the measurements after irradiation have been performed on detectors having completed the beneficial annealing phase.
Irradiation period November '99 (****)
Full size barrell, wedge and miniature detectors were iradiated in this irradiation run, both in the ATLAS cool-box (under bias) and in the PS-shuttle.
Some of the miniature detectors were irradiated in the shuttle up to 4 1014 cm-2.
The detectors were made with oxygenated and standard substrates.
Preirradiation measurements:
I-V's of standard and oxygenated Micron wedge detectors and of the corresponding miniature detectors.
C-V's of some standard and oxygenated Micron wedge detectors
Measurements after irradiation:
IV and CV of MICRON wedge detectors.
IV of miniature detectors irradiated to 3 1014 cm-2 (cool-box, shuttle) and (IV) to 4 1014 cm-2 (shuttle);
CV of miniature detectors irradiated in the shuttle: 3 1014 cm-2 and 4 1014 cm-2
CCE (with light spot from 1060 nm laser) of oxygenated and control miniature detectors irradiated to 3 1014 cm-2.
CCE (with light spot from 1060 nm laser) of oxygenated and control miniature detectors irradiated to 4 1014 cm-2.
 Results (march 2000) with oxygenated silicon vs control material

The charge collection efficiency (from MIP electrons) of large area wedge detectors is here presented for 300 micron thick oxygenated and control and 250 micron thick standard material after 3 1014 cm-2 , normalised to the pre-irradiation value of the charge collection. The normalisation has been obtained by comparing the peak of the charge distribution for overdepleted (500 V) irradiated detectors to the peak of the plateau of the CCE for the non-irradiated detector. This gives about a 10% charge deficit after irradiation. The charge collected by the oxygenated and non-oxygenated detectors after irradiation is about the same for strong overdepletion. This measurements have been done with SCT128 analogue electronics.

LHC-b and oxygenated silicon?

The oxygenated substrate could improve the tolerance of the LHC-b vertex detectors. Experiments are under way in the Liverpool silicon lab, using the SCT128 electronics to compare CCE in non-homogeneously irradiated detectors. A possible scenario for this solution is here discussed.
Here you find some preliminar results of charge collection efficiency and noise for a detector partially irradiate (in the innermost region) with 24 GeV/c protons to 3 1014 cm-2.




x-y table holding an irradiated LHC-b detector

SCT128 data acquisition crate

First Laboratory measurements on a LHCb-phi prototype detector.

A fine spot laser system has been set-up in Liverpool to allow the full characterisation of microstrip detectors. The system is particularly suitable to measure the properties of inhomogeneously irradiated detectors. The inhomogeneous fluence received by silicon sensors during the operation is a concern for the LHCb experiment. Here I put the first draft to resume the results of the measurements on LHCb-phi type detector partially irradiated with 24 Gev/c protons: 14/03/2001 Results with a partially irradiated LHCb-phi type detector.

P-type microstrip detectors (thanks to Moshe Hanlon)

The use of n-strips on p-type silicon for microstrip detectors can extend the lifetime of irradiated devices because of the profile of the electric field. Here I have collected the results with the first succesful n-in-p prototypes.
Before irradiation:
CV of 1728-5 (M. H.)
CV of 1728-25  (M. H.)
CV of 1729-7  (M. H.)
Strip integrity before irradiation (M. H.): 1728-5, 1728-25, 1729-7. 		Results after irradiation (**):
 IV's of 1728-25 and 1729-7
 Interstrip capacitance;  central strip to two nearest neighbours each side
 Interstrip capacitance;  central strip to one nearest neighbour each side, with comparison to pre-irradiation values 
And here is the first evidence (January 2001)of improvement in term of the most relevant performance of particle detectors: the Charge Collection Efficiency (CCE) of an irradiated n-in-p is compared with the CCE of a standard and an oxygen-enriched p-in-n detectors after 3 1014 protons cm-2. The noise performances as a function of bias for the same detector are here shown. The improvement of the CCE is intirely due to the geometry of the electric field in the n-in-p diode structure and NOT to a lower full depletion voltage. This latter is not improved using p-type bulk, as it is shown here after 3 1014 protons cm-2.
CERN RD50: Radiation hard semiconductor devices for very high luminosity colliders
I am the convener of the Full Detector Systems research line of the CERN-RD50 collaboration. To see the scope and the participant institutes to this collaboration click here. I list some of the contribution I gave to the RD50 meetings and workshops:
5th RD50 workshop, Florence, 14-17 October 2004 – Talk
4th RD50 workshop, CERN 5-7 May 2002 – Talk
2nd RD50 workshop, CERN 18-20 May 2003 – Talk
1st RD50 workshop, CERN 2-4 October 2002 – Talk

RECENT PUBLICATIONS AND TALKS
Some of this material has been put togheter for conference presentations and/or articles. Here I list some recent presentations.

 

 

RESMDD'04

…or the 5th International Conference on Radiation Effects on Semiconductor Materials Detectors and Devices October 10-13, 2004, L.go E. Fermi 2, Florence, Italy  You find here the talk.

VCI 2004

…or the 10th Vienna Conference on Instrumentation, Vienna, Austria, February 16-21 2004  You find here the poster and the article.

ERICE 2003

…or the workshop on Innovative Detectors for Supercolliders, Erice (TP), Italy, 29th Sep.-03 Oct. 2003  You find here the talk and the article.

ELBA 2003

…or the 9th Pisa Meeting on Advanced Detectors, La Biodola, Isola d'Elba, 25-31 May 2003  November 3-8, 2002. You find here the poster and the article.

VERTEX 2002

…or the 11th INTERNATIONAL WORKSHOP ON VERTEX DETECTORS, Ohana Keauhou Beach Resort, 78-6740 Alii Drive Kailua-Kona, Hawaii  November 3-8, 2002. You find here the talk and the article.

ELMAU 2002

… or the  9th EUROPEAN SYMPOSIUM ON SEMICONDUCTOR DETECTORS, New Developments on Radiation Detectors, Schloss Elmau, June 23 - 27, 2002. You find here the article.

ISM2E-YS

... invited talk at the International Symposium of Young Scholars on Mechanical and Material Engineering for Science and Experiments, 11-16th of August 2001 Changsha, Hunan Province, China. Here you can find the transparencies of my talk.

4th STD

... or the 4th International Symposium on Development and Application of Semiconductor Tracking Detectors (Hiroshima, March 22-25 2000). I have presented a comparative study of oxygenated and control Si diodes, miniature and full-sized microstrip detectors. Here you can find the transparencies of my talk.

RD 99

... or the 4th International Conference on Large Scale Applications and Radiation Hardness of Semiconductor Detectors (Firenze, Italy, 23-25 June 1999) I have presented some results concerning changes in interstrip capacitance and noise in microstrip detectors made by Micron on 6" <100> substrate or by Hamamatsu on 4" <111> substrate.
Here you can find the article.

Radecs 99

....or the 5th EUROPEAN CONFERENCE: Radiation and its effects on components and systems (Abbaye de Fontevraud, FRANCE, Maine et Loire, 13 - 17 septembre 1999).
I have presented some results concerning p-type detectors and oxygenated material to the Radecs 99 conference.
Here you can find the poster  and the article.

If you want to take a look to my thesis (again on silicon detectors)

PhD thesis (Université Joseph Fourier - Grenoble I, France):
The effect of hadron irradiation on the electrical properties of particle detectors made from various silicon materials.
N.B. Text is in english.

My Publication List.

For comments etc. please contact Gianluigi Casse

Contact Informations
E-Mail:  <gcasse@hep.ph.liv.ac.uk>
Phone:  +44 151 794 3399
Fax:  +44 151 794 3441 		Postal Address:
University of Liverpool - Department of Physics
Oliver Lodge Laboratory
Oxford Street
Liverpool L69 7ZE
United Kingdom
Last modified: 20/03/01