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\section{Specific Instrumental Developments}
\subsection{Detector Developments}
\subsubsection{Detectors for E00-110 (DVCS) and E03-106 (nDVCS)}

Contributed by P.~Bertin, C.~Hyde-Wright, A.~Camsonne, C.~Mu\~noz Camacho, F.~Sabati\'e and E.~Voutier
for the DVCS/Hall A Collaboration.

\vskip 1.cm

During the past year, the E03-106 DVCS experiment on the neutron (nDVCS) was proposed and
approved by the PAC and will most likely run just following the proton
experiment E00-110, currently scheduled to start in august 2004. In addition
to the construction of the E00-110 detectors, a tagger system is
being constructed especially for E03-106. The next few paragraphs will
detail the status of readiness of each subsystem for both experiments:
the custom scattering chamber and detector support, the electromagnetic
calorimeter, the scintillator array, the nDVCS tagger, the data acquisition
system and finally the DVCS analysis software.

The E00-110 experiment needs a custom scattering chamber which will allow the detection
of protons with momenta as low as 400~MeV/c. A 62~cm-diameter, 1~cm-thick spherical aluminum
has been designed for this purpose, and is planned to arrive at Jefferson Lab on april 2004.
The DVCS detectors attach to a frame, which itself sits on a support structure, attached to
the Big-Bite moving frame. Both the DVCS detector frame and the support structure will
be at Jefferson Lab in december 2003, much before the installation of the detectors on 

The electromagnetic calorimeter is composed of 132 blocks of PbF$_2$ stacked
in 12 columns of 11 rows. This detector was assembled during the summer 2003
and tested thoroughly till the end of 2003. First results from cosmic runs
show that the photo-electron yield
is above the Monte-Carlo expectations by about 20\% with about 1200 p.e./GeV. The
LED monitoring system showed promising performances after some necessary tune-up.
Some repairs and improvements need
to be done and it is planned to take the calorimeter apart, repair it and re-stack it
in january 2004.

The proton/neutron detector consists in a 100-blocks scintillator array. The blocks
are truncated trapezoids, arranged in 20 towers of 5 scintillators each. Each tower
spans $13.5^\circ$ in azimuth around the nominal virtual photon direction.
Each scintillator in a tower spans $4^\circ$ in polar angle.
The scintillators are coupled to XP2972 PMTs. 
In order to cope with the large background of low energy
particles in the proton array, we are constructing 
an active base with the first two dynodes stabilized by a 
Zener diode/transistor circuit, and an electronic pre-amplifier of gain 30
(V. Popov, JLab). We will operate the HV in the range 
650 to 800 V, (PMT gain $3\cdot 10^3$ to $3\cdot 10^4$). The
total signal amplitude from DVCS protons ranges from 300 to 3000
photo-electrons. The towers, fully equipped with PMTs and electronics
are expected to be ready for installation in february
2004. The mechanical support for them is already available.

The nDVCS tagger is composed of 2 layers of 2~cm-thick EJ200 scintillator paddles.
Each layer is segmented in 20 elements corresponding to the 20 towers of the
scintillator array described earlier.
The second layer is shifted by 1.5$^{\circ}$ compared to
the first layer to avoid dead areas.
An additionnal 1~cm-thick iron plate provides an additional shielding to the tagger
from the direct view of the target.
A prototype scintillator paddle was mounted and tested at LPSC Grenoble in order to
improve the response of the detector in terms of light uniformity across the paddle.
It was found out that short light guides were necessary to improve the response,
especially in the corners of the paddle.
Also, the wrapping was studied and aluminum foil was
chosen as the best wrapping to shorten the pulse as much as possible, which is
essential in the E03-106 high rate environment. New prototypes with final dimensions
and light guides will be tested before the end of 2003 and the design of the tagger
system will be frozen before the end of the year. The scintillator
paddles are planned to arrive at LPSC mid-march. By then, all the
components of the tagger should be there (mechanical assembly, light guides,
phototubes, divider bases), and the assembly will proceed. The whole detector 
should be ready for tests sometimes before mid-may, the planned shipping 
date to Jefferson Lab is may 31st. This leaves one month to re-mount the
detector and the time between the end of june and the beginning of the
E03-106 experiment in october 2004 for tests.  Note that this schedule allows
for the detector to be mounted in the Hall in its regular setup before both
experiments start, which allows for an in-situ mechanical test.

The CODA data acquisition interface to the ARS, the trigger module(s) and
the XY-table was
achieved in 2003, and was successfully tested with both LED and cosmics for the
calorimeter in the fall 2003. Some software are still needed, among which
the communication with EPICS for the high voltage, XY-table movement and LED setup.
All this EPICS software are currently under development and should be ready by the end
of 2003. The scintillator array and nDVCS tagger have not been plugged in the
acquisition system, since they are not yet constructed. However, much of what has
been done for the calorimeter can be mimicked for the other detectors, since most
components are essentially the same. The next major step is the integration with the
Hall A DAQ, which will be tested during the next down available in the first half of
2004.

The sofware scheme used for the E00-110 and E03-106 experiments resembles the
RCS scheme: the spectrometer analysis will be performed in the first phase, either
with ESPACE or with HANA. The analysed data will be output in a ntuple-like
structure, to be read back by the DVCS software package, which will perform
the rest of the analysis.
The calorimeter offline analysis software is ready and tested with Monte-Carlo
data. Clustering algorithms along with energy and position calculations are
available. The scintillator array geometry is fully implemented and the
proton trajectory through the actual detector can be computed with the
corresponding energy losses and light emission in each individual block.
The ARS waveform analysis is developed but needs to be integrated into the
DVCS software package. Event displays are available for debugging
and online monitoring, but have only been tested with offline data (Monte-Carlo,
cosmics and LED runs). Most of the software efforts in the next few
months will focus on the development of additional monitoring tools, which can
be tested both with offline and online data from cosmics and LED calibration runs.

Overall, the construction phase is on good tracks and we expect to have the whole system -
nDVCS tagger excluded - ready by the end of february 2004 for thorough tests and additional studies.
The nDVCS tagger itself will be ready for tests in june 2004, much before the expected running
date in october 2004.


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