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                                                                   Exhibit 10.33


                                 PROMISSORY NOTE


$10,000,000.00                                             Boston, Massachusetts
                                                                   July 31, 1997


         FOR VALUE RECEIVED, the undersigned Micrion Corporation, a
Massachusetts corporation (the "Borrower") hereby promises to pay to the order
of FLEET NATIONAL BANK (the "Bank") the principal amount of Ten Million and
00/100 ($10,000,000.00) Dollars or such portion thereof as may be advanced by
the Bank pursuant to Section 1.2 of that certain letter agreement of even date
herewith between the Bank and the Borrower (the "Letter Agreement") and remains
outstanding from time to time hereunder ("Principal"), with interest, at the
rate hereinafter set forth, on the daily balance of all unpaid Principal, from
the date hereof until payment in full of all Principal and interest hereunder.

         Interest on all unpaid Principal shall be due and payable monthly in
arrears, on the first day of each month, commencing on the first such date after
the advance of any Principal and continuing on the first day of each month
thereafter and on the date of payment of this note in full, at a fluctuating
rate per annum (computed on the basis of a year of three hundred sixty (360)
days for the actual number of days elapsed) which shall at all times be equal to
the Prime Rate as in effect from time to time (but in no event in excess of the
maximum rate permitted by then applicable law). A change in the aforesaid rate
of interest shall become effective on the same day on which any change in the
Prime Rate is effective. Overdue Principal and, to the extent permitted by law,
overdue interest shall bear interest at a fluctuating rate per annum which at
all times shall be equal to the sum of (i) two (2%) percent per annum plus (ii)
the per annum rate otherwise payable under this note (but in no event in excess
of the maximum rate permitted by then applicable law), compounded monthly and
payable on demand. As used herein, "Prime Rate" means that rate of interest per
annum announced by the Bank from time to time as its prime rate, it being
understood that such rate is merely a reference rate, not necessarily the
lowest, which serves as the basis upon which effective rates of interest are
calculated for obligations making reference thereto. If the entire amount of any
required Principal and/or interest is not paid within ten (10) days after the
same is due, the Borrower shall pay to the Bank a late fee equal to five percent
(5%) of the required payment, provided that such late fee shall be reduced to
three percent (3%) of any required Principal and interest that is not paid
within fifteen (15) days of the date it is due if this note is secured by a
mortgage on an owner-occupied residence of 1-4 units.

         All outstanding Principal and all interest accrued thereon shall be due
and payable in full on the first to occur of: (i) an acceleration under
Section 5.2 of the Letter Agreement or (ii) December 1, 1998. The Borrower may
at any time and from time to time prepay all or any portion of said Principal,
without premium or penalty. Under certain circumstances set forth in the Letter
Agreement, prepayments of Principal may be required.
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         Payments of both Principal and interest shall be made, in immediately
available funds, at the office of the Bank located at 75 State Street, Boston,
Massachusetts 02109, or at such other address as the Bank may from time to time
designate.

         The undersigned Borrower irrevocably authorizes the Bank to make or
cause to be made, on a schedule attached to this note or on the books of the
Bank, at or following the time of making any Revolving Loan (as defined in the
Letter Agreement) and of receiving any payment of Principal, an appropriate
notation reflecting such transaction and the then aggregate unpaid balance of
Principal. Failure of the Bank to make any such notation shall not, however,
affect any obligation of the Borrower hereunder or under the Letter Agreement.
The unpaid Principal amount of this note, as recorded by the Bank from time to
time on such schedule or on such books, shall constitute presumptive evidence of
the aggregate unpaid principal amount of the Revolving Loans.

         The Borrower hereby (a) waives notice of and consents to any and all
advances, settlements, compromises, favors and indulgences (including, without
limitation, any extension or postponement of the time for payment), any and all
receipts, substitutions, additions, exchanges and releases of collateral, and
any and all additions, substitutions and releases of any person primarily or
secondarily liable, (b) waives presentment, demand, notice, protest and all
other demands and notices generally in connection with the delivery, acceptance,
performance, default or enforcement of or under this note, and (c) agrees to
pay, to the extent permitted by law, all costs and expenses, including, without
limitation, reasonable attorneys' fees, incurred or paid by the Bank in
enforcing this note and any collateral or security therefor, all whether or not
litigation is commenced.

         This note is the Revolving Note referred to in the Letter Agreement.
This note is secured by, and is entitled to the benefit of, the Security
Agreement (as defined in the Letter Agreement). This note is subject to
prepayment as set forth in the Letter Agreement. The maturity of this note may
be accelerated upon the occurrence of an Event of Default, as provided in the
Letter Agreement.

         Executed, as an instrument under seal, as of the day and year first
above written.


CORPORATE SEAL                              MICRION CORPORATION

ATTEST:


/s/ N.P. Economou                            By: /s/ David M. Hunter
----------------------------                     -----------------------------
President & C.E.O                                Name: David M. Hunter
                                                 Title: Vice President, Finance
                                                        and Administration



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