Exhibit 10.13

                           THERMEDICS DETECTION INC.
                           -------------------------

                         STOCK HOLDING ASSISTANCE PLAN
                         -----------------------------

SECTION 1.   Purpose.

         The purpose of this Plan is to benefit  Thermedics  Detection Inc. (the
"Company")  and its  stockholders  by  encouraging  Key Employees to acquire and
maintain  share  ownership  in  the  Company,   by  increasing  such  employees'
proprietary  interest in promoting the growth and performance of the Company and
its  subsidiaries and by providing for the  implementation  of the Stock Holding
Policy.

SECTION 2.        Definitions.

         The following terms, when used in the Plan, shall have the meanings set
forth below:

         Committee:  The Human Resources  Committee of the Board of Directors of
the Company as appointed from time to time.

         Common  Stock:  The  common  stock  of the  Company  and any  successor
thereto.

         Company: Thermedics Detection Inc., a Delaware corporation.

         Stock  Holding  Policy:  The Stock  Holding  Policy of the Company,  as
adopted by the Committee and as in effect from time to time.

         Key Employee:  Any employee of the Company or any of its  subsidiaries,
including  any  officer  or  member  of the  Board of  Directors  who is also an
employee,  as  designated  by the  Committee,  and who,  in the  judgment of the
Committee,  will be in a position to contribute  significantly to the attainment
of the Company's strategic goals and long-term growth and prosperity.

         Loans:  Loans extended to Key Employees by the Company pursuant to this
Plan.

         Plan:  The Thermo  Fibertek  Inc.  Stock  Holding  Assistance  Plan, as
amended from time to time.

SECTION 3.        Administration.

         The Plan and the Stock  Holding  Policy  shall be  administered  by the
Committee,  which  shall  have  authority  to  interpret  the Plan and the Stock
Holding Policy and, subject to their provisions, to prescribe, amend and rescind
any rules and  regulations  and to make all other  determinations  necessary  or
desirable for the administration  thereof.  The Committee's  interpretations and
decisions  with regard to the Plan and the Stock  Holding  Policy and such rules









and regulations as may be established  thereunder shall be final and conclusive.
The  Committee  may correct any defect or supply any omission or  reconcile  any
inconsistency  in the Plan or the Stock  Holding  Policy,  or in any Loan in the
manner and to the extent the Committee  deems desirable to carry it into effect.
No member  of the  Committee  shall be liable  for any  action  or  omission  in
connection with the Plan or the Stock Holding Policy that is made in good faith.

SECTION 4.        Loans and Loan Limits.

         The Committee has  determined  that the provision of Loans from time to
time to Key  Employees in such amounts as to cause such Key  Employees to comply
with the Stock Holding Policy is, in the judgment of the  Committee,  reasonably
expected to benefit the Company and  authorizes the Company to extend Loans from
time to time to Key  Employees  in such  amounts as may be requested by such Key
Employees in order to comply with the Stock  Holding  Policy.  Such Loans may be
used  solely for the  purpose of  acquiring  Common  Stock  (other than upon the
exercise of stock options or under employee stock purchase plans) in open market
transactions or from the Company.

         Each  Loan  shall be full  recourse  and  evidenced  by a  non-interest
bearing  promissory note  substantially in the form attached hereto as Exhibit A
(the "Note") and maturing in accordance with the provisions of Section 6 hereof,
and containing such other terms and conditions,  which are not inconsistent with
the provisions of the Plan and the Stock Holding Policy,  as the Committee shall
determine in its sole and absolute discretion.

SECTION 5.        Federal Income Tax Treatment of Loans.

         For federal income tax purposes,  interest on Loans shall be imputed on
any interest free Loan extended  under the Plan. A Key Employee  shall be deemed
to have paid the imputed interest to the Company and the Company shall be deemed
to have  paid said  imputed  interest  back to the Key  Employee  as  additional
compensation.  The deemed  interest  payment  shall be taxable to the Company as
income,  and may be deductible to the Key Employee to the extent allowable under
the rules relating to investment  interest.  The deemed compensation  payment to
the Key Employee shall be taxable to the employee and deductible to the Company,
but shall also be subject to employment taxes such as FICA and FUTA.

SECTION 6.        Maturity of Loans.

         Each  Loan to a Key  Employee  hereunder  shall be due and  payable  on
demand by the  Company.  If no such demand is made,  then each Loan shall mature
and the principal  thereof shall become due and payable on the fifth anniversary
of the date of the  Loan,  provided  that  the  Committee  may,  in its sole and
absolute discretion, authorize such other maturity and repayment schedule as the
Committee may determine. Each Loan shall also become immediately due and payable
in full,  without demand,  upon the occurrence of any of the events set forth in
the Note; provided that the Committee may, in its sole and absolute  discretion,
authorize an  extension of the time for  repayment of a Loan upon such terms and
conditions as the Committee may determine.



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SECTION 7.        Amendment and Termination of the Plan.

         The  Committee  may from  time to time  alter or amend  the Plan or the
Stock Holding Policy in any respect,  or terminate the Plan or the Stock Holding
Policy at any time. No such amendment or  termination,  however,  shall alter or
otherwise  affect the terms and  conditions of any Loan then  outstanding to Key
Employee  without  such Key  Employee's  written  consent,  except as  otherwise
provided herein or in the promissory note evidencing such Loan.

SECTION 8.        Miscellaneous Provisions.

         (a) No  employee  or other  person  shall  have  any  claim or right to
receive a Loan  under  the  Plan,  and no  employee  shall  have any right to be
retained  in the employ of the Company  due to his or her  participation  in the
Plan.

         (b) No Loan shall be made  hereunder  unless  counsel  for the  Company
shall be satisfied that such Loan will be in compliance with applicable federal,
state and local laws.

         (c) The expenses of the Plan shall be borne by the Company.

         (d) The Plan shall be unfunded,  and the Company  shall not be required
to establish  any special or separate fund or to make any other  segregation  of
assets to assure the making of any Loan under the Plan.

         (e) Except as otherwise  provided in Section 7 hereof, by accepting any
Loan under the Plan,  each Key  Employee  shall be  conclusively  deemed to have
indicated his acceptance and  ratification  of, and consent to, any action taken
under  the  Plan or the  Stock  Holding  Policy  by the  Company,  the  Board of
Directors of the Company or the Committee.

         (f) The appropriate officers of the Company shall cause to be filed any
reports,  returns or other  information  regarding  Loans  hereunder,  as may be
required by any applicable statute, rule or regulation.

SECTION 9.        Effective Date.

         The Plan and the Stock  Holding  Policy  shall  become  effective  upon
approval and adoption by the Committee.



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                                      EXHIBIT A TO STOCK HOLDING ASSISTANCE PLAN


                           THERMEDICS DETECTION INC.

                                PROMISSORY NOTE



$                                                            Dated:
 --------------                                                    -------------


         For value received, ________________,  an individual whose residence is
located at _______________________  (the "Employee"),  hereby promises to pay to
Thermedics  Detection Inc. (the "Company"),  or assigns,  ON DEMAND,  but in any
case on or  before  [insert  date  which  is the  fifth  anniversary  of date of
issuance]  (the  "Maturity  Date"),  the principal sum of [loan amount in words]
($_______),  or such part  thereof as then  remains  unpaid,  without  interest.
Principal  shall be payable in lawful money of the United States of America,  in
immediately  available  funds, at the principal office of the Company or at such
other  place as the Company  may  designate  from time to time in writing to the
Employee.

          Unless the Company  has  already  made a demand for payment in full of
this Note, the Employee agrees to repay an amount equal to 20% of the Employee's
annual  cash  incentive  compensation  (referred  to as bonus)  to the  Company,
beginning  with the first  such bonus  payment  to occur  after the date of this
Note,  and on each of the next four bonus payment dates  occurring  prior to the
Maturity  Date.  Any amount  remaining  unpaid under this Note, if no demand has
been made by the Company, shall be due and payable on the Maturity Date.

         This Note may be prepaid at any time or from time to time,  in whole or
in part,  without any premium or penalty.  The Employee  acknowledges and agrees
that the Company has advanced to the Employee the principal  amount of this Note
pursuant to the Company's Stock Holding  Assistance Plan, and that all terms and
conditions of such Plan are incorporated herein by reference.

         The  unpaid   principal  amount  of  this  Note  shall  be  and  become
immediately  due and  payable  without  notice or  demand,  at the option of the
Company, upon the occurrence of any of the following events:

                  (a) the  termination  of the  Employee's  employment  with the
         Company, with or without cause, for any reason or for no reason;

                  (b) the death or disability of the Employee;

                  (c) the  failure  of the  Employee  to pay his or her debts as
         they become  due,  the  insolvency  of the  Employee,  the filing by or
         against the Employee of any petition under



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         the  United  States  Bankruptcy  Code  (or the  filing  of any  similar
         petition under the insolvency law of any  jurisdiction),  or the making
         by the Employee of an assignment  or trust  mortgage for the benefit of
         creditors or the appointment of a receiver,  custodian or similar agent
         with respect to, or the taking by any such person of possession of, any
         property of the Employee; or

                  (d) the issuance of any writ of attachment, by trustee process
         or  otherwise,  or any  restraining  order or  injunction  not removed,
         repealed or dismissed  within thirty (30) days of issuance,  against or
         affecting  the person or property of the  Employee or any  liability or
         obligation of the Employee to the Company.

         In case any payment herein provided for shall not be paid when due, the
Employee  further  promises  to pay  all  costs  of  collection,  including  all
reasonable attorneys' fees.

         No delay or omission on the part of the Company in exercising any right
hereunder  shall  operate as a waiver of such right or of any other right of the
Company, nor shall any delay, omission or waiver on any one occasion be deemed a
bar to or waiver  of the same or any other  right on any  future  occasion.  The
Employee hereby waives presentment,  demand,  notice of prepayment,  protest and
all other  demands  and notices in  connection  with the  delivery,  acceptance,
performance, default or enforcement of this Note. The undersigned hereby assents
to any  indulgence  and any  extension  of time for payment of any  indebtedness
evidenced hereby granted or permitted by the Company.

         This  Note  has been  made  pursuant  to the  Company's  Stock  Holding
Assistance Plan and shall be governed by and construed in accordance  with, such
Plan and the laws of the State of Delaware and shall have the effect of a sealed
instrument.


                                              -------------------------------

                                              Employee Name:
                                                            -----------------


- ------------------------
Witness



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