Scientific Interest and Technical Challenges to observe Gravitational Waves

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Scientific Interestand Technical Challenges to
observe Gravitational Waves

• Riccardo DeSalvo
• LIGO project
• California Institute of technology

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• Hi, my name is
• Marco Polo
• I would like to help opening the road to the
  Gravitational Waves

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Outline

• Astrophysical and cosmological interest of
  observing GW
• Who is doing what
• What China needs to become a player
• What help can China get
• Which relevant issues are at stake

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Scientific interest

• Neutron Stars are the cinders of the Mendeleyev
  table production
• There are many more NS than visible stars
• NS merge into BH, and BH merge into larger BH
  to finally form the immense BHs at the
  center of galaxies

Chandra X-ray observation of IMBH
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Scientific interest

• Hulse Taylor observation of accelerating
  orbiting NS pairs have proven the merger of NS
  and the existence of GW
• Chandra is showing us a wealth of BH in globular
  clusters that are slowed down by dynamical
  braking (equipartition of energy) and will merge

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Scientific interest

• TAMA started the observation of GW with a range
  extending over our Galaxy.

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Scientific interest

• LIGO is now capable to reach beyond Andromeda and
  will cover a radius of 20 Mpc

Kpc
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Scientific interest

• Virgo will soon match LIGO and maybe go somewhat
  farther than that (depending on configuration)
• Adv-LIGO will reach a range of 200 Mpc
  for NS-NS inspiral in less than 10
  years,

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Scientific interest

• An evolution of Virgo may get to Adv-LIGO
  sensitivity in a similar time scale
• LCGT is seeking funding and would have similar
  performances

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Scientific interestsignal expectations

• TAMA had no real hope of observation.
• Present LIGO may be lucky, estimations of NS
  pairs are very variable. They suggest the
  possibility of a detectable signal anywhere
• - from once a year
• - to every 30 years
• Similarly for Virgo

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Scientific interest,signal expectations

• Adv-LIGO will reach ten times farther than
  initial LIGO which is its watch will cover one
  thousand times more universe volume than initial
  LIGO
• Even the pessimistic estimation of one NS
  inspiral signal every 30 years for LIGO gives 30
  signals per year for Adv-LIGO

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Scientific interest

• Lower Frequency underground interferometers much
  netter chance they will
• reach much farther
• be sensitive to much massive objects
• without the need to go in space

See tomorrows presentation
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Scientific interest

• Observed from an underground L.F. interferometer
  the Universe will start blinking and twinkling
  with GW at us.
• GW astronomy will really have started

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Scientific interest, conclusions

• Ten years from now a new generation of GW
  interferometers will observe many inspirals per
  year and start mapping the cinders of our
  creation
• And this does not include possible signals from
  Supernovae, rotating NS (millisecond pulsars),
  inspiralling BHs,cosmic background, and other
  sources that we are not dreaming of.
• Space Time will look quite different.
• Is China going to join the effort?

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Technical challenges

• LIGO requires the readout of position with
  resolutions of 10-18 m 1/1,000 of the size of
  the proton

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Technical challenges

• Future Gravitational Wave Interferometers will
  have even tougher challenges to reduce the noise
  levels 10 or 100 timer lower
• We have to push the technological limit in almost
  all directions

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Technical challenges

• What are the technologies that China has to
  master to the highest level to be competitive?

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Technical fields

• Laser technology
• High power Laser technology
• Ultra stable lasers
• Optics
• Mirror substrate technology
• Mirror coating technology
• Advanced optics concepts

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Technical fields

• Control technology
• Hyerarchical mirror controls
• Multiple interlocking nested loops
• Real time Digital data processing (fast DSP, fast
  and high resolution ADC and DAC)

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Technical fields

• Seismic attenuation
• Passive attenuation techniques
• Active attenuation techniques
• High level metallurgy
• Maraging
• Glassy metals

Virgo 10 year Old Technol.
The future
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Technical fields

• Thermal noise issues
• Ceramic material technology
• Crystals
• Glassy ceramics (Fused silica)
• Seismic sensing
• Advanced accelerometers for Newtonian Noise
  subtraction (for underground facility use or even
  for somewhat improving the frequency range of
  existing surface facility)
• Advanced (highly directional) accelerometers for
  feed back issues

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Technical fields

• Vacuum technology
• Low emissivity materials (specialy steels)
• Quiet pumping techniques (sublimation pumps)
• Large vacuum vessel techniques
• General engineering
• Large structures
• Large excavations
• Cryogenics?

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Technical fields

• Noise treatment techniques
• Extraction of weak signal from large noise
• Mathematical filtering methods
• High speed computing
• Large database and large complexity algorithms
• High speed computers

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What help may be available

• Detecting GW is terribly difficult
• We all need more facilities for coincidence
  measurements, for guaranteeing observation time,
  for triangulation,
• We need diversified facilities to cover different
  kind of sources
• So far the world effort only provides a fraction
  of what would be needed
• Any new contributor is warmly welcome and
  supported as much as possible (see welcoming from
  Cerdonio, Barish, Giazotto, Menzinger)

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What help may be available

• The GW community will gladly host and train
  Chinese scientists to most trade lore
• All design and technologies developed
  specifically for GW are already public and will
  be made available
• Some techniques are classified or controlled and
  some may become so. These will not be available,
  but often special permissions can be asked for
  for specific use of specific instruments.

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What help may be available

• Can China get financial support in the near
  future?
• In my opinion, the answer would probably be NO!
• everybody is busy with scarce resources
• Can China get technical and scientific support?
• In my opinion the answer is YES,
• with some limitations due to national policies,
  but YES.
• The international community will practically
  collaborate with a Chinese GW effort
• (see GWIC statement and other welcomes)

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What help may be available

• It took 30 years for US and EU to get where we
  are
• Collaboration with the international GW community
  can help China to speed up the process
• With international support a Chinese facility may
  become relevant in less than 10 years (see HEP)
• Chinese scientists can be relevant from
  immediately through international collaboration

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What help may not be available

• Examples of possible problems
• Maraging is a material necessary for seismic
  attenuation and suspensions but also for Uranium
  enrichment centrifuges
• Glassy metals may be necessary for the lower
  stages of seismic attenuation, but also are of
  great interest for military use
• Some lasers and metrology systems are strictly
  controlled
• High speed computers are controlled items
• Some nations are more restrictive than others

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What help may be available

• Examples of technical and scientific
  international collaborations on GW
• LIGO and GEO are collaborating across the board
• Virgo and LIGO are collaborating on mirror
  developments and other issues
• LIGO and TAMA are collaborating on seismic
  attenuation issues
• LIGO and SIFM (Shanghai) on sapphire
• Some sort of Data analysis agreements between
  mostly everybody and everybody-else

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What do other players get by helping China?

• Must divide the question in three time scales
• short,
• medium and
• long term

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What do other players get by helping China?

• Short term (even if China eventually fails to
  build a relevant facility)
• If China wants to get in the game needs to train
  its best people
• China will send the best people to be trained at
  the existing facilities, etc.
• By doing so these scientists will contribute to
  the advancement of the existing facilities
• There is a shortage of high level scientists

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What do other players get by helping China?

• Middle term (China builds a relevant
  interferometer)
• Even a single top of the line additional
  interferometer would be precious for online
  efficiency, coincidence, triangulation, signal
  certification, etc.
• Low level coincidence run already in S1, S2 and
  S3 with different partners
• Virgo and LIGO committed to fully share data for
  optimal detection sensitivity and online
  efficiency
• All will gladly exchange significant data with a
  Chinese (or Japanese, or Australian,..)
  interferometer to improve the GW signal reach and
  significance

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What do other players get by helping China?

• Long term (China builds a relevant facility)
• Nobody will commit now to install an
  interferometer in a Chinese facility, everybody
  is fully using their own resources home
• When GW will be detected and
• If China prepares an Underground Facility
• Everybody will want to participate in installing
  a GW interferometer in that facility

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What do other players get by helping China?

• Long term (China builds a relevant facility)
• If GW are detected there will be a rush to cover
  the frequency space
• At Low Frequency Newtonian Noise is the limiting
  factor and the solution is only underground or in
  orbit

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What is needed to be relevant?

• Sufficiently large and long term effort.
• Time to train people
• Time to build facilities
• Sufficient resources to be relevant

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What is needed to be relevant?

• TAMA was the front runner for several years.
• But TAMA is too small to remain relevant

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What is needed to be relevant?

• Now, for lacking of financial support, the
  successor LCGT is delayed and TAMA is becoming
  irrelevant (except for developmental issues)
• In the wait for funding Japanese scientists will
  remain active and relevant through international
  collaborations

TAMA LIGO
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What is needed to be relevant?

• GEO is terribly relevant from the developmental
  point of view
• For lacking of sufficient financial support GEO
  was never really relevant as a GW detector
• GEO found relevance through international
  collaboration with LIGO and later with EGO/Virgo
• Similarly for ACIGA

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What is needed to be relevant?

• Will need patience and perseverance, but what we
  propose is feasible!!!

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What is the issue?

• Gravity Waves detection will open a new window on
  the Universe, unveiling the twisting and
  churning of space-time around black
  holes, telling us about the death and birth of
  matter
• The present generation of GW detectors, LIGO,
  Virgo, and even Advanced LIGO, will tell us about
  the small players, Neutron Stars and stellar size
  Black Holes
• The real players will remain invisible until we
  build low frequency GW detectors
• LISA, the future space based GW interferometer is
  designed for this important job

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What is the issue?

• X-ray emission is detected from matter
  occasionally falling into Larger Black Holes
• Modern globular cluster simulations indicate
  prompt generation 100-1000 sm IMBH from core
  collapse.
• The further accretion of 10 sm BH onto the IMBH
  will be visible only through LF interferometers
• LF under-ground based GW interferometers can do
  this astronomy well ahead of LISA
• Astrophysicists eagerly waiting to hear from us!

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Conclusions

• China is a great country with great traditions
• We all expect China to make great contribution to
  Science
• A leading edge GW detection facility is a very
  worthwhile contribution
• The road to the Grav. Waves is hard and long but
  it is full of great things and we can do some of
  the way together
• I hope I was of use to you.

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• And, while on your way, you can answer some of
  my questions!