The Leading Spectrometer of ZEUS Design, Construction and Performance

Nicolo Cartiglia INFN, Italy and SCIPP (!)

STD06, AbeFest, Carmel, 11th September 2006

• Who, When and Why • Electronics • Beam • Performance

1 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy The Leading Proton Spectrometer Group

The LPS group was a collaboration of 3 Universities: Bologna, Turin and Santa Cruz for a total of more than 50 people. Santa Cruz designed and built the front-end electronics. Many people from SC took part:

E. Barberis, N. Cartiglia, J. De Witt, D. Dorfan, T. Dubbs, A. Grillo, B Hubbard, W. Lockman, J. Ng, K.O’Shaughnessy, D. Pitzl, J. Rahn, B. Rowe, H.F.-W Sadrozinski, A. Seiden, E. Spencer, A. Webster, M. Wilder, R. Wichmann, D. Williams, D. ZerZion

2 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy We built the LPS in 1989-91

Intel CPU 486: 33 MHz. 1.25 M transistor

Windows 3.0 was released in 1989

Earthquake

Abe was my professor of Q.M. There was a wall in Berlin 3 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy HERA Physics

The main goal of HERA is the study of – proton interaction both at high (DIS regime, Q2> 2-4 GeV2) and low (Photoproduction) momentum transfer.

4 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy The ZEUS detector

The ZEUS detector is located on the HERA collider in Hamburg.

It’s a general purpose detector: • vertex •Wire Chamber • calorimeter •Muon Chamber in the return yoke

5 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy ZEUS forward detectors

Forward S1-S6: 6 LPS station, 24- 90 m Calorimeter, 103 m

S1-S3: horizontal bending

S4-S6: vertical bending

6 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy Forward Physics at ZEUS

In some events the proton remnant is characterized by the production of a leading baryon (proton or neutron)

These LBs carry a very high fraction of the incoming proton beam momentum:

xL = pz/p’z ~ 0.95-0.999

7 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy Leading Proton Production

The production of leading differs depending on the

value of xL : fragmentation, reggeon, pomeron.

Note: these names are overlapping processes without a clear distinction 8 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy The ZEUS LPS

•Six detector stations •Each station: 6 single sided Si detector planes •115 um pitch (0 degree) •115/sqrt(2) (+- 45 degree) •Inserted in Roman Pots

Total: •54 detector planes •50,000 channels

9 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy The silicon plane

• 300 um tick Si wafer, p strips on n substrate • 3 manufacturing company: CANBERRA, MICRON, EURSYS • Oval cut, precision on cut- out better than 100 um • Yield ~ 85% • Capacitance ~ 1.2 pF/cm • Depletion Voltage: 30-50 V •Mounted on a 6 layers Cu-Invar support, water cooled 10 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy The Front-end Electronics - I

The LPS detector required a low-noise, low-power, radiation hard front- end electronics: it had to work near the beam with very little space available for the electronics and its cooling.

It was decided to use a binary read-out to simplify the signal to noise problem and implement it using a combination of two chips: an analog amplifier comparator chip, the TEKZ, and a digital memory chip, the DTSC. Requirements: Low Noise: S/N ~ 22 Low Power: < 2 mW/channel Narrow width to match the microstrip Pipelined operation Radiation hardness up to 3 Mrad and 1014 p/cm2 11 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy The Front-end Electronics-II The DTSC CMOS chip The TEKZ bipolar chip

•DC Coupled to the TEKZ •DC Coupled to the detector •Clock freq 10 MHz •Shaping time = 32 ns •L1 and L2 buffers •Gain = 150+-20 mV/fC •FLT pipeline 5 us length •S/N ~ 22 with 11pF load •Power 2 mW/Channel •Power 2 mW/Channel •50,000 Transistor •72 um •1.2 um technology 12 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy Roman Pot

Beam pipe Detector

Roman Pot: 3 mm with 3 movements: μ a 300 m thick window 1. Detector in/out 2. Pot in/out 3. Transverse

Resolver Position accuracy: 5 μm 13 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy Roman Pot Motion

At filling time the pots are retracted

Approaching the beam

Full insertion for data taking

14 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy A LPS station

Mechanical support Cooling pipe

Filters

TEKZ - DTSC Detector 15 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy A real event

16 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy Hit Maps

Empty band: dead DTSC chips

17 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy Detector Performance

The LPS is a difficult detector to Year ZEUS LPS operate: it can only be used with perfect beam condition and no 1994 3 0.9 “creative” set-up 1995 6.6 3.4 1996 11 0 •Noisy or dead channels < 2% •Measured plane efficiency > 99.5 % 1997 28 13 •Noise < 0.3 ch/plane firing per bunch 1999 36 10 crossing 2000 47 35 Lum 132 62 (pb-1)

18 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy LPS Physics Reach

The LPS has been the used in many analysis: (unexpectedly we found ourselves in the middle of a strong competition with on the topic of ‘diffraction’)

•Clean tag of diffractive events, both at low and high mass •Measurement of the t- distribution in various processes (vector mesons, diffraction, high and low Q2 processes) •Clean tag of double diffraction •Leading proton production spectra

19 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy Leading Proton Spectrum

This plot shows the momentum spectrum of leading proton produced in e-p collision. It can be considered the summary of the LPS operation…

Several models are also shown

20 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy Conclusion

The LPS was the first roman pot system operated at DESY. It took data for 7 years with a ~ 60% efficiency and integrated a luminosity of 70 pb-1

The LPS used 50000 channels of single sided Si detector read-out by two VLSI chips that provide a digital output. The 2-chip architecture that was developed for the LPS is now widely used in other systems

21 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy Personal Conclusion

It was and incredible occasion to witness the creation of a high tech lab: I arrived in Santa Cruz in 1989, before any probe station, chip analyzer or other sophisticated equipment. We had a rotary switch to change the gain on a amplifier…and we thought we should go and live in Texas. The lab was ‘the place to be’, long hours and a lot of new ideas. In one of my early day Abe asked me my favourite movies. Before I could come up with a really boring intellectual movie he said: I really like “The creature from the Black Lagoon”…and I understood I was in the right place!

Thanks Abe, Thanks Hartmut! 22 September 11th 2006 Nicolo Cartiglia, INFN, Turin, Italy