Alignment Work in TT2 and PS During the Shut-down 2006-2007

CTC 07/07/2009H. MAINAUD DURAND, BE-ABP/SU1TZ32 tunnelCTC 6/07/2009H. MAINAUD DURAND BE-ABP/SU2

TZ32Tunnel TZ32: 800 m straight in slope LHC depth

Objectives:install long stretched wires and go on performing gravimetric measurements.

But there is a certain amount of studies to undertake in order to access that tunnel and to install equipment inside.

We need a strong support from CLIC!

AP Forum 9 juin 2009T. Dobers BE-ABP/SU3

CTC 6/07/2009H. MAINAUD DURAND BE-ABP/SU4

Gravimetric measurements as well as astro-geodetic measurements are under way in collaboration with ETHZ frame of a doctoral thesis: determination of a precise gravity field for the CLIC feasibility studies.

A first set of gravimetric measurements was performed during Spring 2009 in this tunnel (one profile every 5m). Then this summer, on the surface, one profile will be measured using the same instrumentation plus a zenith camera system and GPS in order to measure de vertical deviation of each point

A second set of measurements will have to be carried out in the tunnel during another season, when the access in the tunnel is possible

Tests/measurements to be undertaken in this tunnel:

Gravimetric measurements

CTC 6/07/2009H. MAINAUD DURAND BE-ABP/SU5

Tests/measurements to be undertaken in this tunnel:

Vertical deviation measurementsWe will need to test and validate instruments for measuring the vertical deviation directly in the tunnel (a system displaced along the tunnel of each linac, measuring the local vertical deviation)

Long term stability measurements of long stretched wiresAs we need to obtain a better knowledge of the parameters that influence the shape of the wire taken as a reference of alignment (temperature, humidity, gravity effects, modelization), a first facility was implemented in an old ISR tunnel: TT1.

The TT1 tunnel has a total length of 150m. Some micrometric, even nanometric measurements are performed (stabilization mock-up). But some civil engineering works are foreseen in 2012 at the end of the tunnel, which are not compatible with the accuracy of the measurements performed.

CTC 6/07/2009H. MAINAUD DURAND BE-ABP/SU6

Tests on long wiresTests concerning the stretched wires need to be undertaken on wires as long as possible, to be as close as possible from the baseline, and to see all the impact of the parameters like temperature or humidity. A 500m wire was stretched in the TT83 tunnel, but even if the wire was protected, the impact of ventilation was important as the ventilation was just in front the wire. TZ32 would be a very interesting solution to perform such measurements.

Test of an alternative optical solution of alignmentThe solution of overlapping stretched wires is the baseline, but an alternative optical solution of alignment is also studied, and will have to be tested on long distances, and compared to the stretched wires solution.

Tests/measurements to be undertaken in this tunnel:

CTC 6/07/2009H. MAINAUD DURAND BE-ABP/SU7

The whole TZ32 tunnel is considered as a ventilation duct for the LHC. If we want to install equipment inside, we need to install a real ventilation pipe, whose diameter will be smaller than the tunnel. The 3.2. area of the LHC will be quite radioactive. If the ventilation has a smaller diameter to evacuate the air, this will modify / increase the level of radiation going out of the pit. The maximum admissible value concerning radiation level at the pit was specified in the INB documentation, and cant be changed. So studies have to be undertaken in order to determine if the new smaller diameter of ventilation still fit in the radiation requirements. Then, the new ventilation system must be rad hard and optimized from the dose emittance point of view for people working in the tunnel.

The tunnel is a straight line: nothing prevents the radiations from spreading in case of a loss of beam. A thick shielding should be added on the LHC side of the tunnel. Studies should be undertaken in order to determine its thickness to allow work on the first 500m of the tunnel (from the PM32).

The access doors should be modified to allow an access in the tunnel from the PM32 (and not from the tunnel).

Problems to solve before working in the TZ32: